Back in 2018 there were some changes made to use boss1's UNIT_TARGETABLE_CHANGED event to init the timers. Boss UnitIds are not available in wotlk classic, so these timers never initialize and only show up once abilities first get used.

I tried to do some testing but /etrace causes fps issues and that's not ideal for a timed boss, so I only checked it quickly and the event only seemed to fire for nameplate1. I doubt this will fire if someone has nameplates hidden, so likely another solution is needed (maybe reverting to previous init logic for classic).

Edit: I see that for months now it's no longer using "boss1" but rather registers the event for all units and checks the mob ID. No clue why it doesn't initialize the timers

We would need a full log from the Transcriptor addon to further analyze what's going on here. Also if I recall correctly the very first pull is different to subsequent pulls, so we'd need a log of both a very first pull and a subsequent pull.

Transcriptor_alga_nonfirst.txt

I forgot to enable it for the first pull, for the subsequent pulls this should work fine (renamed .lua to .txt to attach)

tr_alga.txt
Also made this one from 10man. This includes 1st pull, as well as some others, but I forgot to switch it off afterthe kill. There should be 2-3 non-first pulls in there properly split.