Removing paint from teak is often a futile idea. The problem is the paint gets way down in the grain and you gave to sand off a lot of wood to get past it. So much wood in some cases you change the dimensions of the trim piece, window frame, etc.
We've tried it with some painted door panels on our boat and found out the hard way what's involved.
If one wants to paint over teak that would otherwise be finished bright, the teak should first be varnished (or use sone other bright finish) and then paint over that. Then if the current or a future owner wants to return the trim, window frame, etc. to bright the paint will not have gotten down in the grain.
Modern consumer finish removers are virtually worthless they are so weak. They will soften the paint and then smear it around as you try to remove the paint with the result that the paint gets forced down even farther into the grain.
I used to refinish gunstocks for gas money when I was in college. There were finish removers available then that would actually penetrate walnut and lift an oil finish out of the wood. They were so stong that if you got any on your skin it would immediately start to burn and you had only moments to wash it off before things got serious. But they were fantastic finish removers. By comparison the finish removers available to consumers today are about as effective as spit. I know-- we've tried them all. I assume this is due to nanny state regulations protecting us from ourselves.
Now if you take your window frames to a commercial finish removal shop they may be able to lift the paint out of the grain because they can probably still use reall strong, effective strippers.