I am beginning now with some celluloid repairs, and I have an issue. In order to restore missing material, I have made a putty out of similar-color celluloid and acetone. When this cures, some very small holes appear in the repaired surface.
I understand that this "bubbling" is typical of celluloid and acetone repairs, and that replacing acetone with MEK should help. My question is about the already repaired pens. Should I try to fill those holes with more putty, or will the bubbles appear again?

How big are the bubbles versus the rest of the new material?

4 pokes 1/8 mm wide, maybe, in a surface of 4 mm.

Julikko,
Could be related to the viscosity of your putty.
The more viscious your putty, the more air enclosure risks during application.
Also the application thickness of the layer could be involved.
Applying several consecutive layers - with drying intervals - will be less risky for air enclosure in my opinion.
I expect the point holes can be easily filled up again with putty.