Hi Dippndots, unfortunately we were not able to reproduce this issue (using 3ds Max 2018 and newest daily build of Corona).
If you are able to reproduce it consistently, could you please provide exact steps about what you are doing and what happens, preferably in points?
Here is what I tried:
1. Set the main output to xxx.tif, selected 16-bit (tried with both 16-bit options).
2. Then set up LightMix so that all required elements are created.
3. Set pass limit.
4. Then submitted the job to BB.
5. After the rendering, the files were correctly saved in the specified location.
6. Opened the tif files in PS.
7. They are all 16-bit.