If it's only with DropBox, maybe try some other solutions ?
I believe maybe the problem is on the combo of Apple and DB, as i did earlier have a guy that run TC for win in a MAC/ Parallell system and he also have a lot of crash/ problems until he changed to PC instead of MAC.
And he did use sync function in DB in both cases.
V18, V19, V20, V21, 2015/ 16/ 17/ 18 Pro. Platinum
Deluxe V20, V21, 2015/ 16/ 17
Windows 10 Home Premium 64 bit, 32 GB
NVIDIA Geforce GTX 780m, 1 GB