I'm dealing with the same issues with my right hand. You don't mention which grip you use, but one thing I've found is that I can't generate sufficient grip strength with the thumbs forward grip that's all the rage these days. I've switched back to the old thumb over thumb revolver grip with my semi-autos, and it has made a huge difference. Just a thought.
Thanks for commenting. I do lock my thumbs down, and place the support thumb over weapon hand thumb, with revolvers; always have.
I also locked my thumbs down when using SIG P229 pistols, at least when shooting right-handed, to keep my thumbs away from the side latch. (I got away from the high-bore-axis SIGs, and the .40 S&W, as soon as my chief OK’ed 9mm duty pistols, in 2015; I transitioned to 9mm Glocks.) I would fire my SIG P229 pistols with both thumbs forward, when shooting lefty, as the slide latch is not in the way of my thumbs. I do the same with Glocks, up to and including Gen4.
The Gen5 Glocks have that stupid slide latch “paddle” on BOTH sides of the weapon, which gets in the way of my right support hand performing that trendy high-on-the-frame, thumbs-forward support method, when shooting lefty. The base knuckle of my right thumb clamps right up against the slide latch paddle. Trying to keep my right hand clear of the “paddle” causes the whole support hand grip to decay into uselessness. For whatever reason, that does not happen when shooting right-handed, but notably, my hands are not mirror images of each other.
Perhaps, if I want to seriously use my Gen5 Glocks, for two-handed left-hand shooting, I’ll have to grind-off that stupid “anti-ambidextrous” slide latch paddle, to get it out of the way of my right support hand. This will also allow me to use my older Glock holsters, which were not made to accommodate the Gen5’s “ambidextrous” slide latch lever.
I always fired my 1911 pistols with my weapon-hand thumb oriented forward, on top of the safety lever. I do not remember when I started using the higher support hand grip with my support thumb forward, on 1911 pistols.