If you are going to perform any kind of maintenance works which could disrupt your quorum cluster-wide (e.g. network equipment, small clusters), you would have learnt this risks seemingly random reboots on cluster nodes with (not only) active HA services. 1
To safely disable HA without additional waiting times and avoiding long-term bugs (which Proxmox do not care for 2), you will want to perform the following:
Once (on any node):
mv /etc/pve/ha/{resources.cfg,resources.cfg.bak}
Then on every node:
systemctl stop pve-ha-crm pve-ha-lrm
# check all went well
systemctl is-active pve-ha-crm pve-ha-lrm
# confirm you are ok to proceed without risking a reboot
test -d /run/watchdog-mux.active/ && echo nook || echo ok
Reverse the above, so on every node:
systemctl start pve-ha-crm pve-ha-lrm
And then once all nodes are ready, reactivate the HA:
mv /etc/pve/ha/{resources.cfg.bak,resources.cfg}