my mine drops down to 410-415GH. I would rather keep it running and pay a deposit so he would ship a new controller out and refund me after he receives the bad one than shut the miner down for a week or two.
It may not be a controller issues as from your description.
Are you seeing any "x" or "-" in you asic status page?
Give me your Ant S3-es fans speed, temperatures of miner and ambient temperature?.
Most probably its, the heat dissipation issue and the chip are throttling to lower clocks automatically as in GPUs.
As already advised by bitmaintech support engineers, unscrew the chip side heatsink and check the condition of thermal grease.
Remove it with a cloth and apply new thermal paste grease and it will be mining back at 441.
Use a good thermal grease which provide conductivity above 3.