We have reviewed few reported cases and found that there is a potential bug that affects the system stability. I suggest upgrading to the firmware below which fixed the bug.
https://download.peplink.com/firmware/plb30/fw-b20_30-8.1.0s083-build4956.bin
For those still having stability issue with this firmware, please help to open ticket for us to investigate. We may need to check the device usage and other factors.
Thank you.