I can confirm is a stale party indeed, flushwork seems not very good. Got a huge rate of stales.
I think the flushwork is some weird cron job. Both my Jupiters showed the flushwork line at the same exact time
I do not think it is doing it intelligently
They seem not to be handling well the flush work at pools request, they are sending a lot of bad work and hence the stales and the lower hashrate especially on the pool