So you have otg USB ability?
You are not using any "work arounds"?
It destroyed this phone, from the get go and Verizon has agreed to replace it.
Glad Verizon is replacing your phone since you're having problems...but all 3 of our DT2's have been working beautifully with Marshmallow, and also with the latest tiny OTA update Verizon pushed this week.
I hadn't actually tested with OTG until you raised the question, but thought to check it out since you asked. I haven't used OTG in the while - not since my Galaxy Nexus. So my OTG adapters are a few years old. The best I had back then was from Samsung:
ET-R205UBKG
I tried several USB thumb drives with it, and they all work quick nicely. I get a notification with a topic such as "Kingston USB drive" with a subheading, "For transferring photos and media". I can select the notification, explore, and see files in a list view or a grid view. It also offers to show me System Volume Information, which includes IndexerVolumeGuid and WPSettings.dat.
I tried copying a folder with a few dozen PDFs in it from my laptop onto the thumb drive, plugged the thumb drive into the OTG adapter, and was immediately able to browse and view the PDFs. I had forgotten how incredibly convenient this can be. Great to be able to carry something like a 64GB or 128GB flash drive and use it either with the laptop or the phone, although I already have a 64GB SD card in the phone (looking to use a bigger one as the prices keep dropping).
The one thing that didn't work via OTG, and that I didn't expect to work, was when I plugged my 2TB Seagate Plus Portable Drive into the OTG adapter. I got an error - the phone reported the drive as "corrupted" and offered to fix it. But knowing that the phone doesn't have the power to operate a 2TB mechanical portable drive, and might, in fact, need an app like StickMount to make it work, I did NOT allow the phone to make an attempt as "fixing" my Seagate backup drive. But again - I didn't expect this to work, and it's not a big deal, since I it appears than USB flash drives are working just fine via OTG support.
Anyway - to your question - yes, OTG support seems to be fine with Marshmallow on my Droid Turbo 2. All 3 of our DT2's are working beautifully with the updates, all are on Marshmallow, nothing was lost, damaged or corrupted.