I’m afraid I was completely wrong!!
Current, power, and energy use 32 bits, so 2^32 is the maximum value for them (65532^2).
65532 would be the limit for 2 bytes. I mistook nibbles for bytes…
So, if energy resets to zero above 65,532kW, this would indicate the soft is only getting 2 of the 4 bytes, as 4eyes said
(I noticed the error when I read 4eyes said the maximum value for current would be 65 amp, when the module is specified for 100A)
BTW, PZEMs firmware does not take full advantage of the main IC’s capabilities (V9981). For example, according to the datasheet:
https://www.javanelec.com/CustomAjax/GetAppDocument/84d8dfa1-17fe-4430-8ccc-e6a7901446f8
There are registers for positive and negative energy accumulators (page 269) but the module does not provide information about imported/exported energy