@tsachi , thanks for your help.
I have decided to reinstall the betanet node in directory n_beta1, see the steps above.
The old n_beta node still fails. I don’t think it is worth to investigate the failure any more.

~$ cd n_beta1
~/n_beta1$ ./algod -v
12885164034
3.4.2.beta [rel/beta] (commit #b56953f4)
go-algorand is licensed with AGPLv3.0
source code available at https://github.com/algorand/go-algorand
~/n_beta1$ cd ../n_beta
~/n_beta$ ./algod -v
12885164034
3.4.2.beta [rel/beta] (commit #b56953f4)
go-algorand is licensed with AGPLv3.0
source code available at https://github.com/algorand/go-algorand
~/n_beta$