LTO Tape Transfer Issues - normal transfer speed but slow verification, and pauses

Tried 3.17 and 3.8.5 with IBM LTO6 drive, LTFS, Windows

Two questions

1. In both cases writing ~100 10GB files went well at expected LTO6 speed at 160MB/s

But verification of data is very slow at 80-100MB/s

Any explanation and how to improve this

Async file transfer DISABLED

System write cache ENABLED

2. Sidenote: when writing to LTO, every now and then roughly every 200GB, the transfer pauses for a while and less than 20 seconds later, transfer resumes - and at full speed. Doubt its shoe shining

Any tips to modify the options and etc so I can get the best out of the software?

Many thanks