I had got this problem at least twice, and reported it once.
Now even v3.2.4 seems have the problem.
I plugged external HDD which contains truecrypt container file that size is 64GB.
And after doing other thing (note: if I immediately mount the container, then I succeed. an interval is needed to reproduce this), tried to mount it via Truecrypt.
Then, it says the file is used.
Obviously the culprit is saappsvc.exe which consumes a littele CPU and seems to be holding the file and never (I waited more than 30 min) release.
I stopped all other unnecessary applications, and even stopped all other SAP services except SAP App Whitelisting Svc which is unstoppable and the culprit.
Please look into it, maybe SAP has problem to handle quite large file?
The container file actually don't have any file types but I named it with .vhd extension.