RData environment empties on project startup

When I open a project (which has a saved environment in the .RData file - sometimes up to a couple of Gb) in RStudio it often (but not always) starts with an empty environment and clears the RData file to 32B. I have Global and Project options to Restore RData into workspace and also Always Save workspace on exit. I am opening the project using the drop down menu in the top right hand corner of Rstudio.

R version 4.0.3 (2020-10-10) -- "Bunny-Wunnies Freak Out"
Platform: x86_64-pc-linux-gnu (64-bit)