That is (was) a known issue with CHR in VMware (or similar):
http://forum.mikrotik.com/t/routeros-7-9-2-x86-disk-issue/167122/1
Post some details on the hardware you are using, it is possible that for some reasons the USB LTE modem is (also) detected as a disk, at each reboot and/or every time the LTE is disabled or enabled, 1785 seems to me a very high number both for reboot and for failover switches, anyway, so maybe the adding of the disk slot happens on other events too.
Or maybe you have some kind of periodically running script that creates the problem?
Setting through a scheduler a script that removes that entries once a day/week/month should be relatively easy, but it would be better - if possible - to find the root cause for that behaviour.
It would be a good idea if you also post your configuration, following these instructions:
http://forum.mikrotik.com/t/forum-rules/173010/1