Figure out high bandwidth source?

Hello! I have a RB750 to route my small business traffic and since last week I’ve noticed some huge upload peaks (25-90mbps) during dawn and evening when the office is closed, and I can’t figure out how to block it or where it comes from (since all PCs are turned off)

The weird thing is: this peaks sustains for like 30seconds, stops for one hour, and then it hits again. Even more weird: my uplink with my ISP its only 8mbps, how can I get 80-100mbps traffic at my gateway (pppoe-out)?
When this traffic hits my internet connection just “drop” (can’t open any website or ping anything outside my local network)


by the way, I use PCQ Queues to limit everybody download/upload to 4mbps. it works very well but doesn’t seem to work in this particular case.


PPPOE-Out (gateway) graphic:
7ea627f6-1cc8-4ef6-9674-3c1d9479079a.jpg
daily (1).gif
Does anyone have a hint for me?
Thanks!