Problems with OpenWrt on my router

My router is TP-Link TL-WR845 v4, which is very similar to TL-WR841N v9 (same CPU, switch), except for appearance, flash(1M) and RAM(8M)
So I mod my device, make it 16M flash + 64M RAM and flash OpenWrt 18.06.0 for TL-WR841N v9.
It works well for most of the time, but sometimes problems occurs and I cannot find out why.
For example, sometimes I cannot find the WiFi and I have to unplug and plugin.
Or, sometimes my network connection become too slow to bear. When I tried to login via SSH, it tells me that 'connectrion refused on port 22' sometimes. Even if I login successfully, I am experiencing a huge lag and I have to reboot it manually.
I tried to disable uhttpd and slow down the CPU frequency, but it won't help. What can I do?

run a memory test for a few hours
verify your hardware mods are working before blaming software

Could you be more specific?
The output of 'free' command

root@OpenWrt:~# free
             total       used       free     shared    buffers     cached
Mem:         60360      27544      32816         96       2132       8352
-/+ buffers/cache:      17060      43300
Swap:            0          0          0

For example

if you have a serial connection you can check if U-Boot or whatever bootloader has a memory test "mtest" and run that to verify you new RAM works without errors. If it fails then that is the problem.

Is the device this is occuring on running Windows 10?

  • If so, that's a known bug in Windows, and disabling and re-enabling WiFi on the Windows device should fix the issue, else a reboot of the Windows device may be required.

Yes, I am using Windows 10 right now. However, when I cannot find it on PC, I also cannot find it on my Android phone.

To troubleshoot, you're going to need to read the system log when it occurs:

  • Issue: logread && logread -f
    • Once you issue the command, disable and enable the WiFi on each device, give it a few seconds, and watch the log to see if any handshakes occur.
      • If none do, read up through the log output to determine when the affected device(s) were disconnected, checking to see if anything happened prior to, or right after, the disconnect that would explain the disconnect.