I noticed this as well, maybe it waits until they are confirmed or something, not sure.
Payments have been well above fees though at least.
hum, my fees are higher then mining at S4. Im negative at -0.0014222. A few days ago they stop giving the compensation

Hi,
S4 mining revenue is assigned by PPLNS payout, which is subject to pool luck. If it takes too long time to find a block, it is possible to get a negative mining profit per the payout of each block found. But it should be a positive balance every 24 hours.