Had same problems, locking files, no sync after quitting office365 applications. Luckily I first tested it with the free version. All solved after going back to 2.3.8. Updates are almost immediately, don't even have to close excel. I cannot understand how Resilio can be in such denial of this elementary problem... not syncing correctly... Any other issues to be aware of with the older version? Or better to forget about sync completely?