I've found that unless the ambient is less than 30C the Whatsminers will never finish their tuning mode and as a result will run slower.
Not the case with M21s, I managed to run this in extremely hot days (beyond 40c) and honestly it runs way cooler and much better than MOST bitmain gears, but I understand that different models/batches will perform differently.
Yeah, I couldn't figure that drop from 45T to 30T out; the tuning process seemed to have completed successfully because there is a flag in the web interface that indicates when tuning completes.
What was the voltage they ran on? the way you desribe the issues tells me that your miner's PSUs weren't so happy with the voltage they had, either too high or too low.