Is there a way of stopping Impress reformatting my presentation?

I am using LO Version: Build ID: 1:6.0.7-0ubuntu0.18.04.10

I have a presentation that I am saving as a .ppt file and every time I open it the formatting changes. This particularly occurs in tables. I set the padding to 0.2 all around the cell, and choose single-line spacing and then save it. When I reopen the presentation the padding has gone and I am back to what appears to be random proportional spacing that results in lines of text overlapping/being far too close together, and what appears to be completely random font sizes. I would be really grateful for any help with this! I just need Impress to leave the formatting that I have done alone.

Problem as always:

saving as a .ppt file

Save as an Impress file and there won’t be any changes.

Write a feature request / report a bug.