Been there, its the lug on backside of TS. Lube it and somehow hold the TS in the mid position, while gently tapping the right hand side of the axle of TS. It will eventually back out, will need to continually move the business side TS lever up and down while tapping. After removal , install the TS in a bare frame and examine lug interference with frame cutout. Thats more than likely where the problem lies. Doing this its only the frame and TS, then add one ignition part at a time. Be aware, forcing the blocking lug of TS onto the sear can lock it up as well.
When you are satisfied TS lug is clear in frame cutout and all ignition parts installed, without grip safety installed and hammer at full cock, install TS, blocking lug should contact the sear and NOT completely install. This where you scribe a mark and begin to slowly remove material from TS blocking lug. GO SLOW the thumb safety needs to move up the sear without moving the sear at all, but blocking lug of TS must touch the sear!!
I use my 10-8 armorers block to securely hold TS while assisting in removing material in correct angle on blocking lug. I've been told it can be accomplished by being vigilant to retain exact angle on blocking lug. This will take several tries to get it correct. Leave a bit on blocking lug so you can stone to a smooth finish
No room for error here, if blocking lug doesn't touch sear when in the up position ( again without moving position of sear at all) it is not safe. Period.
Do you know the safety checks for this condition? If not cock pistol, put safety on and with approx twice force necessary to fire , depress GS and pull trigger. Hold pistol near ear and gently pull hammer further down. If you hear a faint "click" too much material has been removed from TS blocking lug. This is an unsafe condition and a new TS will need to be ordered. Most of us have done this, its part o the learning process
This isn't rocket science, and sorry if my instructions make it seem difficult. However, if install isn't exact, pistol isn't safe. After removal is achieved, study TS fit in your bare frame. Once it moves fully and without interference, install ignition parts and attempt to install TS, it SHOULD NOT install all the way ( btw grip safety is not installed at this time) and you will clearly see where locking lug of TS needs work. Good luck