Android loses the default route. How to solve the problem?

Question

Android

Android loses the default route.
Internet goes down every 10-15 minutes. At the same time, the wi-fi icon is on. On the mikrotik router (others also tested), everything is fine in the logs. The problem is not related to changing MAC addresses (they do not change). In this case, local resources are pinged and are available both by domain name and by IP. The Internet does not respond and the tracer is empty. I checked the routes and everything became clear, except how to treat it!
What routes look like with the Internet:

Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask		MTU	Window	IRTT                                                       
wlan0	00000000	012110AC	0003	0	0	0	00000000	0	0	0                                                                              
wlan0	002110AC	00000000	0001	0	0	0	00FFFFFF	0	0	0                                                                              
wlan0	002110AC	00000000	0001	0	0	318	00FFFFFF	0	0	0                                                                            
wlan0	012110AC	00000000	0005	0	0	0	FFFFFFFF	0	0	0

With absence:

Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask		MTU	Window	IRTT                                                       
wlan0	002110AC	00000000	0001	0	0	318	00FFFFFF	0	0	0

Answer 1

first you need to reduce the circle of possible culprits of the problem, in this case there are 3 of them:
first you need to see if a similar problem is observed with another phone in the same conditions, preferably with the same OS version. If there is no suitable one, you can check it on another router with the same phone. If there is no problem on another router, then it’s not a fact that the problem is in the phone and you need to check the router already (reset settings and reconfigure or connect another one).
If the problem remains, then the problem is in the phone, here it can also be divided into 2 possible reasons:
In the first case, there may be a problem with the power saving mode or power management, in the second, a problem with the firmware or some kind of left application in the background.
Both the first and second can be checked if you reflash to a newer firmware or simply reset the parameters.

Answer 2

provider - no other devices work no problems.
router - no, I tried other same problems, again, other devices work, there are no problems.
phone - no tablet. It clearly has problems.
The problem appeared immediately. I used a day without third-party software out of the box, so to speak. Other users with this firmware also have a problem. There are no other firmware. Resetting settings didn't help.

Answer 3

Does the device receive routes via dhcp or static?
Is your wifi twitching?
Is there any third-party software that can change the routing (VPN client for example)?