If you did your best, I don't see sandbagging as a problem, other than feelings hurt (like yey we won, oh wait, we didn't). Do the best you can, post when you want, it's part of the whole thing. Sometimes it's not even sandbaging per se, rather a safe score so that you at least have a submission if the hardware die on you. I think most people then actually do bench to the last second.
I'm used to this since we had Swedish Championship every year like 10 years ago, and it was the same back then