After retrieving Zeek metrics in Zeek 8.0, running them through promtool check metrics results in complaints about zeek_msgthread_pending_messages_in_buckets and zeek_msgthread_pending_messages_out_buckets.

zeek_msgthread_pending_messages_in_buckets non-histogram metrics should not have "le" label
zeek_msgthread_pending_messages_out_buckets non-histogram metrics should not have "le" label

Both of those metrics are of type "gauge". This issue appears to have originated with Zeek 7.1.