How can I find the cause of the memory leak?

Hello.
How can I find the cause of the memory leak? Typically, there is approximately 65 MB of free space remaining during long-term operation. Recently I noticed that there are 14 MB of memory left for 10 days of work. The last thing that was changed: DNS server on the router is enabled and DOH from CloudFlare is enabled. Before that, DOH from Google was enabled and there was no such problem. But after Google’s DOH started working with errors, I changed it to DOH CloudFlare.

Router: hAP AC2, 128 RAM ( RBD52G-5HacD2HnD )
Firmware: 6.47.10 long-term
Screenshot_2021_06_19_22_14_16_135_com_mikrotik_android_tikapp.jpg
UPDATE: 2021-07-06:
The moment the router auto-reboots, when the RAM is almost over (see screenshots)
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Log:
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Screenshot_2021_07_06_03_08_26_953_com_mikrotik_android_tikapp.jpg
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