Painting Balsa

Alittle off topic but maybe someone can help.
I build RC boats from balsa.
Boat #1
Built the boat.
Used Krylon primer till the grain was filled.
Painted with Krylon paint.
Then krylon clear.
1500 grit and polished till light glass.
6 months later the paint was Crazed everywhere.

I thought that maybe I didn’t let the layered set long enough.
SO…
At this point the boat cured almost a year.
I 600 sanded, krylon clear again, worked it till like glass, 6 months later, Crazing everywhere.

Boat #2
Same process only I let the color set for 3 months before clearing, worked it to a glass finish and 6 months later, Crazing everywhere.

What gives?
How do I fix it and prevent it next time?

how is it crazed?

looks like broken tempered glass.
It sat for monthes in primer and again in color without any problem.
The clears seems to be the problem.
But I don’t know.

hhhhhhhmmmmmmmmmmm… have you tried other clears?