When a repeater is powered from the side by a comparator, it locks like a normal locked repeater, but it doesn't get the bedrock bar on it, until you update the repeater.
Linked issues
duplicates 1
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Comments 3
Dupe of MC-9194
MC-72520
Repeater doesn't show "Lock" when locked by Comparator
Resolved
Duplicate
0
CocoaMix
(Unassigned)
Unconfirmed
Minecraft 1.8
Retrieved
After a bit more experimenting, I found this most commonly happens when the repeater is locked by a "subtraction mode" comparator