It wont come back on until your powerwalls get to somewhere between 90-97%. The frequency shift is actually to turn off the solar because "there is no grid" to backfeed to, which is what happens in a power outage situation.
Thing is, many home electronics dont like frequency that high.
Tesla is aware of the issue and should be able to help you if you call tesla energy support. I suggest saying something to them like"
"Hello, I noticed when my system is off grid, it shifts the frequency to 65 hz. which causes my battery backup devices to alarm, my microwave to behave strangely and my lights to flicker. I understand that in cases like this, you can lower the frequency to something that still shuts off the solar but doesnt affect my equipment. Can you please lower the frequency for me?"
They may ask "which brand backup devices do you have. I have cyberpower ones which were impacted by this, so you could tell them you have cyberpower ones (even if you dont). They likely will only lower the frequency down to 62hz or even 62.5 hz but thats still much better than 65hz which many things cant tolerate.
Anyway, they will have to escalate it for you (the tier 1 person on the phone wont be able to lower the frequency) and it may take 7-10 days or so, but they will let you know when its done and you can test again.