Thank you for the details. We have contacted this pool operator. This seems to be a problem with this particular pool.

Please recognize that Proof of Work (PoW) mining efficiency will go down as more blocks are found by Proof Of Stake (PoS). So don't be surprised to have more difficulty finding blocks by PoW, even when the nominal difficulty is low. For example, the nominal PoW difficulty right now is 0.293. However, the difficulty realized by PoW miners is approximately 0.9, due to competition from PoS, which is responsible for 21 of the last 30 blocks (at 274729). No preference is given to PoS minting relative to PoW mining, but over time, the amount of eligible stake will go up, resulting in a greatly increased competition from PoS minters.

It is getting near the point in EBT's life cycle that creating new coins is probably easiest done by buying EBT from an exchange and letting it stake to mint transactions. That minting becomes more efficient relative to mining over time is a designed property of PoW/PoS coins like EBT.