Update: So I have downloaded TG 4.3 to see if I can reproduce the bug now that I am on the same version, and fortunately, I cannot.
TG loads the large erosion just fine, even manually loading it. Additionally, I can handle the ERD and a TER of the same land at the same resolution (though TG's copy is only 5xxmb due to I am guessing lack of maps and extra data).
Total TG is holding 5.3GB of Memory, so it is using 1.5GB Commit and, so if I save/load anything at this point I experience extremely slow wait times while Windows handles files from RAM and SWAP.
So I'm not sure what the issue is on your system. How big are the erosions?
Edit: I do notice some odd behavior. I loaded another project, my "Highland Mountains", and the plugin loaded the terrain, however, in the actual plugin it did not load the file according to it's "Read Now" input field, which was empty. So I loaded the file manually to see if this is where the bug is encountered, but it was able to load the 50km erosion though.