Are seed bags supposed to be used up by planting, or are they multiple use.

They seem to vanish when used, but reappear a little later as though the client thinks they're gone and the server doesn't?

They are used up. Can't say I've ever had this (and I've done a hell of a lot of planting). If you place a seed bag and you have soother seed bag of any kind in your inventory, it will automatically move it to your hot bar. Very useful fur placing blocks. Less so for seeds.

Yeah the times I've seen it the plant didn't grow so I guess the action registered on the client but not the server. I think it might be through planting something when conditions aren't right as last time it happened was at night.

I've seen this glitch (with rose seeds don't know if that's useful to know) during the day.

And yes. The moving to hot bar is a pain imho but I sort of can see why they coded it that way...

I think the moving to hotbar thing is an interaction with another mod, the one that auto-replaces worn out tools from your inventory. It also seems to move stacks of material to your hotbar too, which can be a help when building. It just uses too vague a comparison. It also seems to treat all IC machines as equivalent too.

Seed bags? Hot bars? Worn out tools?