Chain Suck/Chain Slip

[remdog]

I had really bad chain suck after a muddy race, lubed the chain again, then replaced the chain, lubed it once right after putting it on and again in the morning (it was sram and they come a lil sticky) and now it still happens but only in 2-8, and 2-9. derailer and cassete look fine

[DownCycles_Stef]

Try checking for bent teeth on your middle ring. Or even an overly sharp ramp or pin. I've found that on some RaceFace rings for instance, I need to grind the pins/ramps a little to get truly smooth shifting.