dhcp1 deassigned Internet stops for smartphone customers randomly

Hello guys
I have a network of some buildings.
It’s got more than 400 people.
They all have smartphones.
Very few have a laptop.
A problem came up a few days ago.
The Internet stops some randomly.
Although all customers work with Bypass.
I removed all the settings.
And the MIKROTIK settings are starting to be reconfigured.
But the problem is still
I looked a lot, but I couldn’t figure it out.
I tried too many things, changed cables, and I checked all the buildings.
There’s no problem with a cable or device.
The problem may be settings or a new update
Note on the log page these messages
dhcp1 deassigned 10.0.1.xxx
That didn’t exist before.
CCR1009 user device
I’m using the main transmitters from UBIQUITI.
In-building routers for customers are from different companies such as TPLink and tenda and Huawei and others
anybody can help?

anybody can help .