I think it likely has to do with how it was installed or reinstalled before you do it.
The fiberglass is cut by hand from the factory so the hole is not really perfect for starters.
The window may be the double with the escape
window on one side and if it is the bottem section of the window that sits on the fiberglass on that hatch side may want to snag on the fiberglass.
in the Trill' are also framed in wood between the shell and the window and that wood can rot and cause swelling which makes it a little tricky to get the window out.
What I do is remove all screws and use a painters 5way tool or other sturdy flat wide blade to seperate the window from the fiberglass scoring the sealant all the way around.
You may want to remove the outside latch hardware from the escape
hatch side of the wondow as you can picture it protruding into the space where the window meets the edge of the opening and maybe catching on it there.
Then using two people pull and push the window to determine where it is still stuck with sealant to the fiberglass.
Use the bladed tool to pry the window from the outside working around the window from the outside in a circle while the person inside pushes the window away from the area you just pried on.
The window will pop free when this is done but you may have to lift clear of the bottem fiberglass to get it out.
If the factory grey putty is what you are removing from this should be rather simple.
If these have already been sealed before with Butyl Rubber then may "God" himself help you!.
On the other hand....if they have butyl you will not need to be doing this anyway.
I have done all the windows
on two different trills and had no big problems with this,it just takes patience cutting the sealent first till the window comes free.
I then put the window upside down on a flat surface and remove the sealent from the window and do the same from the fiberglass before checking the wood and remaking/replacing if needed.
Getting the sealent off the fiberglass can be the tough part.
It really just takes time.
It is worth doing right,the results are great.
Hope this helps