Breaking-in time of skins on fiberglass congas?

I mounted a thick Cuban cow skin on this Matador fiberglass conga in December
and it is still difficult to handle when it comes to tuning: the pitch drops about a note
anytime I hit the skin in center with my fist - not as playing technique, but to make sure
it sits evenly and the tone is stable. So the skin does not hold the pitch constantly.
Now I wonder if this somewhat instability of the desired pitch is due to the construction
of the drum or is it rather the skin that needs more time?
Should I perhaps even crank the conga up for a while and leave it at a higher pitch?
Or would it be wise to unmount the skin, wet it for some time and mount it again?
I am not really sure what to do.
Other than that, I like to play this Palisades park & Matador combo very much.
and it is still difficult to handle when it comes to tuning: the pitch drops about a note
anytime I hit the skin in center with my fist - not as playing technique, but to make sure
it sits evenly and the tone is stable. So the skin does not hold the pitch constantly.
Now I wonder if this somewhat instability of the desired pitch is due to the construction
of the drum or is it rather the skin that needs more time?
Should I perhaps even crank the conga up for a while and leave it at a higher pitch?
Or would it be wise to unmount the skin, wet it for some time and mount it again?
I am not really sure what to do.

Other than that, I like to play this Palisades park & Matador combo very much.