What conversion kit,
Have you polished out the bolt guide rail yet?
L cut or not L cut type hammer firing pin contract pad on hammer, and have you replace the FCG hammer spring with a reduced hammer spring yet?
Note, why the conversion kits do not come with one to start with, only god knows.

Short of the upper receiver being crushed from using clam shell clamp without the insert piece if play, to causing the bolt to rub on the  inside walls of the upper receiver, then comes down to how well the bolt can glide on the mods, and the tension that that hammer may be placing on the bottom of the bolt as it moving in the upper

And yes, even with the bolt rail polished, still need to replace the hammer spring in the lower with a reduced tension one for the 22 lr conversion, or the rig will only cycle correctly with hot ammo like CCI  minimags.  Once this is done, then check the hammer contact pad again to bottom of bolt, since bolt bottom, or hammer sides may need to be polished to prevent the forward bolt binding.

Next, drop the mag to make sure its not the mag that is sitting too high in the mag well, and causing the mag lips to drag on the bottom channel sides of the bolt.  Hence follower in the mag should be pushed down by the bolt as it comes back until is returns forward, but not the actual side lips of the mag isntead.

Last one, remove the charging handle from the rig,and see if its the bottom ledge of it, that is not high enough for the assembly to clear it.  

P.S, pressure plug will help on accuracy, if you have a 223 barrel in play to hold the assembly all the way forward in the upper.  
And if you are playing the swap game with 22lr, then going back to 223 time and time again, keep in mind that some point, going to need to pull the FSB to clear the lead clogged barrel gas port, and the FSB and even gas tube, from the lead that is shaved off the bullets by the gas port in the bore. Hence lead will build up enough to block the gas action at the front of barrel, and rifle is going to become a single short with shooting 223 ammo through it.

Would have not cut the Gas tube, but rather just ball end milled the top front down on the adapter to make the needed c channel clearance isntead.  
Here is a bore buddy, and you can see the added top full square cut to it, to make the needed clearance for the gas tube to begin with.



On light primer strikes, need you to measure the bolt recess in the bolt for depth.  Myself, tend to go with Anschutz match depth of .038" on any bolt, while something even in the .040" range should works fine.  If  .042" over more, which is thicker than any know Lr ammo rim size, then face of bolt may need to be face milled, to shorten the depth of  face channel.

Also, check FP protrusion (FP and fp rebound spring are consumable parts), since may need to pull the bolt apart, and clean up any burs that are not allowing the fp to fully protrude from the start (if FP is not just worn out from use, or the FP rebound spring has broke), if the case channel in the is not the problem in the first place.  Hence with bolt face channel more then .040", then going to be breaking the FP a lot more than normal. Also, FP is a rebounding type, which means that hammer is not driving it all the way forward completly, but instead spring holds FP back, hammer hits it to start it forward, then momentum carries the FP deeper into the channel to strike the rim in the end. so if spring is broken, will not hold FP far enough back for hammer to send it intinal foreward for a clean full distance movement.

also, really want to use a lightened hammer spring so the rig is not so ammo sensitive in regards to cycling, and even with such, light strikes to cause failure to ignite are not a problem, and you do get longer life out of the FP and its rebound spring, since hammer is not trying to kill both by over pounding them in the first place.  Hence FP does have a stop point, and if channel is too deep, FP does not have the correct protrusion, then stronger hammer spring, or more hammer mass, is not going to make a difference.
Note, some kits like the bore buddies do offer different kit recoil springs to dial in the kit for less powerful ammo to start with, but as stated, stock 223 hammer spring is play, does cause the too much pressure on the FP spring to begin with, so like deal with the problem at the hammer spring first, then if needed for say lighter shooting sub sonic ammo, then you can go after the kits recoil spring.  To add, the buffer spring has play in the works, since it and the buffer should not recoil, since their functions with the kit is only to hold the kit all the way forward in the receiver alone.


To add, might want to check the ammo as well, since during the shortage a while back, a lot of ammo manufacturers had problems with primer compounds that where not igniting correctly.  I bring this up, since my go to less expensive ammo to run is the Fed value packs,

And they had a few lots of such that had primer compound problems that would not ignite correctly, that they were taking back, and replacing with new replacement ammo.


Lastly, the Buffer is supposed to hold the kit tight forward in the receiver, but some times they are not tight, with the back of it far enough back in the receiver for the buffer to hold the kit all they way forward in the first place, and where the pressure plugs come in, to add the extra bit length for the buffer past the buffer retainer pin to keep it tight forward in the receiver.

Or, since its the buffer retainer pin that will dictate how far forward the buffer can go forward in the first place, off set buffer retainer pin does allow the buffer to come more forward, if back of kit is not flush with back of receiver so stock buffer in it forward postion can hold the kit all the way forward in the receiver.

On yours, looks like top of it was too high to start with, and could have either just ran a flat end mill to remove a touch of the top entire edge like the one I posted,


Or where yours has the rub line,  could have just run a 1/4" ball mill down the line to channel cut enough of the top out with a mill, so the gas tube would not bind on the top in that area.



Hence with the gas tube cut now, would need to replace the gas tube and index it correctly to the 223 carrier gas key, to get the rig to run again with 223 ammo.