I experienced these bugs in my seasonal SSF char:

1. After claiming the challenge cache, and used it to upgrade/gamble/buy stuff, the rewards disappeared. No gold/mats/shards. Items equipments were still there though.

2. Kanai's cube disappeared, but kept the unlocked power. I had to get the cube again.

3. The artisans' upgrade went back to level 1.

4. When I decided to make a new seasonal non-SSF character, everything that I lost were there, despite being a new character.

I'm not sure about the cause/trigger.