@BrianGragg tyvm, seems to have solved my problem. Working as intended, since I added the condition you suggested.
Here I got the next one. The following react:
[CODE lang="yaml" title="Save pullers life"] MageCoHPuller:
action: /multiline ; /stopcast ; /xtarget set 13 puller ; /target id ${Spawn[${Me.XTarget[13]}].ID} ; /alt act 7050
condition: >-
${${Group.Puller}.PctHPs} < 80 && ${Me.CombatState.NotEqual[COMBAT]}[/CODE]
is meant so save the pullers life by launch a CoH on the mage in case he's hindered to turn back to camp
but creates a flush of repeating messages on the mq2-window as soon as I reload react with this one enabled:

the undefined Variable is the char-Name of the puller
the first part of the condition "${${Group.Puller}.PctHPs} < 80" may be the culprit, it's the only part, I made myself. The other parts are snippets, already elsewhere in use
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The following modification eliminated error messages:
[CODE lang="yaml" title="save the puller"]globals:
PullerHP: "${Group.Puller.PctHPs}"
MageCoHPuller:
action: /multiline ; /stopcast ; /xtarget set 13 puller ; /target id ${Spawn[${Me.XTarget[13]}].ID} ; /alt act 7050 ; /g Emergency-CoH emminent
condition: >-
${React.Global[PullerHP]} < 80 && ${Me.CombatState.NotEqual[COMBAT]}[/CODE]
next step is, to extend by checking puller.rooted and puller.snared