One of the mystical things around hdmi is that the sink (target of the signal) may talk to the source back, for instance which resolution and framerate it supports (or prefers).
Hence a dilemma for splitters. Two sinks on one source could lead to different preferences. There is no algorithm for determining the least common denominator. Often these splitters declare one of their outputs to "master" (which then decides over the final driven resolution) and the other as "passively driven" with a Take-it-or-leave-it decision to the "slave" output. Others leave the source alone to decide, others do bind all participants to fixed resolution and/or framerate.
If there's damage to your grabbers you could simply test by using them without the splitter again. Okay then?
That would be the first i'd try. Hope you have not damage due to static of the three participants.
The second try would be then to alternate the two grabbers on the output side. Then you should consult the documentation to the splitter regarding the valid formats and resolutions it supports (and to which side). The final step would be to drop and substitute the splitter by another model.
Sometimes simpler models do better job...