What will happen if A3 is triggered & immediately A1 is also triggered?

For mute call best remedy is to improve DL sinr instead of shifting traffic.
Also fine tune tdiscard timer at pdcp.
For traffic part it’s good to shift from high band to low band having more coverage but with above points.
Other part to improve HO failures, also increase % of maxgbr traffic limit on cell.

If neighbour cell become unavailable for which A3 reported then network will not configure PCI of that neighbour in RRC connection reconfiguration and UE will try again for next series of event as per radio condition but it can’t be guaranteed to be A1 or A2 or A3 all depends on event config to UE and matching criteria.

After getting target cell unavailable.
At first it will try to latch with Source cell, if it wouldn’t, then cell reselection process will initiate.
In this case UE event type will be again.
Because previously A1 is to stop measurement and still measure was not completed due to target cell unavailability.

It may be due measurement gaps.

Then the HO interfreq/interRAT will not happened. That value can we use if we want to share load between cells with different frequency (MLB scenario). So HO interfreq load based shall be immediately triggered. IMHO

Is there reference parameter settings for the same?