Filling Joints

I can't claim this work as my own unfortunately.
Made by my grandfather we are told as "therapy" when recovering from the trauma of the 1914-18 great war.
About 10 or 15 years ago I sanded off some old flaking varnish and applied a few coats of Danish oil.
Maybe that was the wrong thing to do but I will be advised if that is so.
The issue now is that there are some fine cracks along some of the joints, maybe from shrinkage.
The small pieces are glued to an unknown timber product, could it be ply from that period?

So do I leave it alone or attempt to fill the cracks and if so what with?

Regards
Bob

Hi Bob. It looks like an important keepsake in your family. I am guessing a bit but I think that the old varnish that you have removed had actually sealed out any influence from humidity in the atmosphere. The application of the Danish Oil has sealed the surface off and is allowing the timber to draw in moisture as it sees fit. Had you used a clear polyurethane varnish I think that you wouldn't have the problem.