Onkyo TX-NR905 HDMI Board Crud

I am replacing a failed standby power transformer (seems an often enough issue on these Onkyos) and have come across this crud accumulated at the inductor and connector solder joints of the HDMI board. I am going to clean this up, but was wondering why it got there in the first place and whether this buildup is something that can cause issues with operation. Onkyos from that vintage had HDMI problems that were blamed on the main DSP chip, solved apparently by reheating it, but I did not have this issue, though I never did run video through it. I had random shutdowns for a period of time and then total failure to come on and found that the primary on the standby transformer was open and am replacing that now.
 

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That looks like an adhesive. Or something spilled inside. My bet is an adhesive.

Remove the adhesive best you can, it reminds me of that corrosive "Sony bond" they used on PCBs.

That tiny mounting location was the standby transformer???? Really? They are normally much larger and mounted on the chassis or a large PCB mount transformer.
 
This is the HDMI board, there is a separate board for standby power with the transformer on it. There may be one other location on the three boards I removed that have this black gunk. It mostly, but not completely, wipes off with isopropyl and a swab.