Wood Filler Epoxy Recommendations

Marine Tex is awesome but you probably won't be able to stain it if you need to

Should accept paint easily

I used a product called PC Woody on a rotten windowsill. Their rot petrifier was very effective. The epoxy putty, though, was very hard to work with. It was extremely sticky. After I’d get my gap filled, I’d slide the putty knife over the area one last time to smooth over the top, and it would pull all the putty out of the void, and I was basically starting over. After doing that 3-4 times, I made the huge mistake of simply leaving the putty proud of the surface thinking I’d sand off the excess after it set up. The stuff was nearly impossible to sand after it got hard. I should have continued to get it smooth with denatured alcohol on a rag while it was still unset.

If you have some mechanical abilities cut it out and replace it. Should be able to exactly match the dimensions of the frame & and stop if is involved. Then a light putty for the seam and paint. Will look better than trying to fill a large section.