Recently bought a G47 and picked up a Glock 1/2-28 threaded barrel for it.  Already had a G34 Gen4, G48 and G43x in 9mm.  After breaking it in for about 500 rounds, I tried it with a couple suppressors.  Worked fine with factory ammo and 147gr. loads with slower powders like CFE Pistol and Autocomp.  However, quieter handloads like a 147gr. with 3.4gr. Titegroup would not lock back on the last round.  165gr. Xtreme with 3.0gr. Titegroup wouldn't even eject (betting it would also struggle with 165gr. Hush).  The G34. G48 and G43x run these loads flawlessly with their factory recoil springs.  G43x and G48 have factory triggers.  G34 has a Timney Alpha trigger.

Tried breaking in the G47 more with a few hundred more rounds.  Cleaning it really good (complete strip down), re-lubing it and even over-lubing it.  Still not dice with the Titegroup loads.  Bought NDZ 15 lbs. and 13 lbs. recoil springs.  The 15 lbs. improved things a bit.  Got it down to the odd failure to lock open with the the 147gr. load and the 165gr. load would eject, but not lock open.  The 13 lbs. recoil spring wouldn't bring the slide back fully into battery.  It would pick up the round and push it into the chamber, but it the barrel was still tilted and not locked up.

I finally gave up on the G47.  It worked fine with factory 147gr. ammo, so I couldn't sent it to Glock for warranty.  But, it irked me that it wouldn't cycle quieter loads that work in all of my other 9mm Glocks.  So, I traded it in for a G17 Gen5.  I put the same Glock threaded barrel in the G17, gave it three mags of break-in and then tried the Titegroup loads.  G17 works flawlessly with the Titegroup loads like of my other 9mm Glocks!

Just thought I would share the experience for those considering the G47 as a suppressor host if they plan on running some of the quieter subsonic handloads in it.  Maybe I just got a lemon(ish) G47, but I'm guessing the shorter recoil spring and slightly heavier slide are a factor.  I don't know, it's only a sample size of one.

147gr with 3.4gr Titegroup should be very decidedly subsonic (as in: you should have some headroom to take it up a bit to generate a bit more recoil impulse and still be subsonic).
That is probably the first thing I would try assuming your velocity is ~900ish

I don't need to, it runs perfectly in the G17 and all of my other 9mm Glocks.  Heck, it even runs in my MPX and CMMG RDB AR upper...

As mentioned, I traded in the G47 for the G17, so it's not possible anyway.

My g47 runs fine suppressed with all my handloads (sub and super). No recoil spring mods.

I much prefer the g47 due to the shorter (g19) recoil spring. It gives ample clearance for the ez lok thread adapter wrench flats.

I'm not using titegroup currently, but I'm using midwest mp190 and cfe pistol. Runs just fine and plenty reliable. I did have some stove pipes when the gun was new, but I shot a couple hundred rounds through it and that seemed to "wear" it in.

If it runs factory and some of your handloads fine, but not others, I'd peg your TG loads as the culprit.

Maybe a dumb question, but was this testing done suppressed?

3.6 grains TG is max load for 147gr, according to Hodgdon.  That's what I use with a plated RN or XTP.  900+ FPS and runs great in my P80/G17 with 17lb spring.  Also runs fine in a 1911 and RDB AR9, all suppressed.

Yes, mostly with an AAC Ti-Rant 9M, and a bit with a TBAC Fly 45.

Glock 17 system has more leverage to cycle the action.
Some say they recoil more than a Glock 19 due to more slide mass bla bla. I tend to agree.

However, in a Glock 17 gen3, swapping out the recoil spring assembly for a .40 cal assembly, seems to be sweet spot.

You added a few variables to the mix by swapping parts and working up handloads. Comparing it to a longer recoil system is apples to oranges.

I’ll add this:
Most Glock failures I’ve seen were improper grip. Especially when training.

Has OP had training?

Do you hold your pistol like James Bond or James Yeager?

I think the the Gen3 G17 (9mm) / G22 (.40SW) use the exact same recoil spring assembly.  

Question for OP, did you replace your O-ring in the booster assembly?   I read that it was lubed, and apologized if I missed o-ring maintenance.

Yes, replaced around a month ago.  Both cans work flawlessly with the Titegroup loads on the G17 Gen5 I swapped the G47 for, and also on the G34 Gen4, G48 and G43x I have.