Thanks for all these detailed advice and explanations. Unfortunately - the baffles are in the best condition, the holes are regular and round.
I think experimenting with additional pressure on lenses to deform them in a controlled manner is a last resort. As the discussion of thermal conditions has shown, changes in temperature could possibly affect the final result and possibly even break the lens.
Perhaps it's worth trying the lens rotation method mentioned by Chip. Honestly speaking, I do not have high hopes for it - it seems to me that it helps to reduce spherical or chromatic aberration, but is it able to help compensate for the defect of the lens geometry? It must be remembered that it is present when the lenses rest almost loosely in the cell, there is no firm pressure on their edges.
Bad luck ... The easiest way would be to try return this telescope to the seller. But I've put more than 2 weeks of work into it, cleaned it, changed the grease, completely disassembled the entire mount, removed the damaged paint from the tripod, sanded it for a few days and brought it to a state where it was possible to expose the natural texture of the wood. It was really hard work and I can still feel it in my spine and aching muscles in my back :-(
Edited by LukaszLu, 14 February 2021 - 12:01 PM.