Format table in Frame

When i want to have a table locked on the bottom of the page i use Frame and paste my tabel in it. Now the Frame deletes all the formats i had in the table. When i change it back, save the document, close it and open it again all my changes i made in the tabel are gone. How can i change the text fonts and alignment and save these, without Libre Office deletes them again?

I have Libre Office 6.1

Assuming I understood correctly: I cannot confirm this with V6.1.1.1RC.
The hard formatted table pasted into a text frame keeps everything, also if the document was stored, closed, and reloaded.
Did you already try to reproduce the reported behaviour bypassing your user profile?
(> Help > Restart in Safe Mode)

I wonder if the new table “styles” could be involved. I’ve had problems with formatting getting reset seemingly at random until I removed all properties from the stable style. Been avoiding them since then.