well, go figure:
today i brought a different gateway (RAK2245) to where the triple-downlink-generating (ADR) node is sending. after starting it up it received the uplinks fine, no downlinks there - TTIG still returning triplets.
climbing up to the attic i found the TTIG (as others mentioned) is flashing it’s LED. checking it’s power supply i found it was a 1A, which i assumed might be a bit on the weak side, so i thought i’d try hooking it up to the raspi, which itself is powered with 2A only - but who knows … lo and behold - for several minutes the TTIG returned single downlinks only.
coming home now, opening the console for the two gateways unfortunately we’re back at triple downlinks from the TTIG. whereas the other gateway seems to sometimes try to take over the ADR-control and sends a downlink by itself instead - a single one i may underscore.
so yes. to me these triple-downlinks look like an issue of the TTIG (though being all but logical, as - as @cslorabox mentioned in another place - shouldn’t be able to “invent” downlinks by itself … but quite obvioulsy, something one could interpret like this is happening.
might bring the node home where i have “classic” TTG, curious if this would behave the same way.