I found that factorio crashes when trying to move items on a space platform. I made it crash by trying to move a crusher and a sonar panel too - it crashed both times.

I'm on version 2.0.20 (build 80511 expansion, win64).
I have the following other mods enabled:
- Quick Map Tag Teleport
- Elevated Rails
- Quality
- Space Age
- Factorio Library

ok. do you have an error message / stack trace? I have an idea but would need a stack trace to confirm.

If you are on the experimental (2.0.21) release, please try 2.4.1; this changes the way entities are moved.

Also getting the freeze while moving entities on space platforms. Strange that it was doing fine earlier then suddenly it instantly freezes server and eats up all system memory. Could not get a stack trace. Happened on factorio version 2.0.15 originally but also 2.0.20.

Perhaps starting happening when Platform got to a certain larger size?
Edit: Not directly related to Platform dimensions but seems related to how much is built on it.

Thanks for the report. What version are you on? I added some code in 2.3.0 to ensure safe movement of fluid entities and that might cause problems. With the 2.0.21 release, there is a new API that made all those workarounds no longer necessary so the 2.4.1 release should resolve these problems (it works fine for me on space platforms).

Also, it would be useful to know what entities you were moving around.