What is the reason for such large delays in the network?

Question

Computer networks

The problem appeared quite recently. The fact is that I periodically began to notice very large delays in data transfer (~ 3400 ms). At first sinned on the provider. Rostelecom all the same, but noticed a trend: when the phone is disconnected from Wifi, the delays disappear. and immediately.
If you connect again, delays do not appear immediately, but after 10-15 seconds after connecting.
Latency was measured by ping on a laptop connected via wifi. Android phone, not rooted. Android 5.1. Everything is fine with other networks. The problem does not recur all the time, but only occasionally.
What could be the reason, or is it just a coincidence and the provider is buggy?

Answer 1

weak connection of the phone with the point, the point lowers the speed, the channel is loaded ...
Well, something like that;)