Metric `validator_monitor_prev_epoch_beacon_blocks_total` always 0

[p2p-sergey-y]

Description

Hello! I found out that metric validator_monitor_prev_epoch_beacon_blocks_total always shows 0 regardless of real block produces. For example, in ropsten validator id 101918. We can see that it produce last block at 10th August, 10:59 PM. Now, how looks validator_monitor_prev_epoch_beacon_blocks_total and validator_monitor_beacon_block_total metrics in grafana (last one works fine):

So validator_monitor_beacon_block_total catches a new block, but validator_monitor_prev_epoch_beacon_blocks_total doesn't.

Version

$ docker exec -it lighthouse_node lighthouse --version
Lighthouse v2.5.1-df51a73
BLS library: blst-portable
SHA256 hardware acceleration: false
Specs: mainnet (true), minimal (false), gnosis (true)
$ docker image ls | grep light
sigp/lighthouse                            v2.5.1    23b9d4a8c9d1   8 days ago     274MB

Present Behavior

Metric validator_monitor_prev_epoch_beacon_blocks_total always shows 0.

Expected Behavior

This metric should set the gauge to 1 then it saw a new block in previous epoch from monitored validator.