I’ve noticed this problem while running bridge mode interface configuration with dynamic VPN. Routed interface mode never experienced this issue. What happens is after approximately 2 days block 80 depletes to zero and all management connectivity to ASA except console becomes unavailable. At some point block 80 can even replenish itself by a small number but eventually, it will fail.
The immediate fix is to reboot which is very disruptive and requires manual intervention from the local resource.
Apparently, this is due to a bug which affects different release versions and is related to either dynamic and multicast routing being enabled on ASA. Both are unsupported features in conjunction with IRB and the only workaround is to disable it. I had multicast routing enable and with disabling it issue was resolved.