I had the same in ver 2018. Excepction caused by mserver.exe in MSVCR120.dll
Problems started with ver 2018.2.1 upgrade and Windows 10 home upgrade 1809. I did it in parallel so cannot trace back what was the root casue. Windows 10 upgrade 1809 changed the way apps have access to the various user directories so that might be the case.
In fact, switching on Local Security (tools-> security->local security) gives permission denied error to the user\ maple\toolbox\ forder and subfolders regardless of read write permissions , set on OS level or maple level. Suggestions from Maplesoft FAQ don't help too.
What I additionally noticed is that libname always starts from maple home directory ("C:\Program Files\Maple 2019\lib") followed by user directories like toolbox etc.
My final workaround is:
1 define libname to put Physics Updates first followed by maple home lib directory and then rest of toolboxes.
2. switch off local engine security (from tools) this is default btw.
3. Start upgrading from maple cloud - this refreshes all files in Physics Updates toolbox directory except Physics Updates.maple , the latest has to be manually downloaded and copied (with name change).
No other side effects were notcied in maple.