In module calibration we have noticed issues with DR0 and DR1 when the crystal tuning was off by 10 KHz
We have noticed the same, and have been working with Semtech on that.
LoRa should be capable of handling frequency error of +/-30kHz (specifically 25% of the 125kHz BW) and during our regression testing we saw a narrower window in SF12 (DR0).
Semtech released a patch for SX1301 HAL a couple of days ago and it corrects this back to +/-30kHz for SF12.
I’m confident it will have a demonstrable affect on the issues seen in this thread.