All 4 zpubs are backed up 4 times physically + on the signing wallets, if someone loses his backup you can still ask the other signers to send the zpubs. I don't think this is a real concern. 
Even if someone completely loses his signing device plus backup, you can start all over by sending coins to another wallet. I will be checking in s few months if all other 3 signers are still with their full setup. 

purpurato

bitcoin

Multisig is easy and you should use it

Most individuals DO NOT need multisig.

This point is critical:

> Physical backups for the 4 wallets are needed, not just one. You need both the seed and the zpubs.

Some people think if you lose one xpub you are fine because you still have the others. To the contrary, if you lose just one, you are sunk.

If you have any question in your mind whatsoever, do not attempt. All you will achieve is to increase the odds that you will lose your funds.