I have encountered the same issue multiple times (only with E2EE meetings) and still have no clue why this issue appears in the first place. So far it happens to guest/external users. For example, if the host puts a guest in the "waiting room" and then re-admits after some time, the guest can't join the meeting anymore and gets this error 70 stated as "network issue". Afterward, neither guest nor the internal user can join the meeting and the meetings require to be restarted by the host, once the meeting is restarted, both internal and the guest users are able to join the meeting without any issues. Have you encountered this issue on a specific version of Zoom or on multiple versions?
I've been trying to find an answer online, but I got nothing so far. Very enigmatic thing is that this only affects 25% of all the E2EE meetings.