The bug

Turtles that are already in love mode and have already or are mating with another turtle, can still be targeted by a third turtle for breeding. Causing a "double pregnancy" with double the amount of sand digging particles and all three turtles falling into the breed delay.

How to reproduce

1. Get some sea grass
2. Find 3 turtles on a beach
3. Feed turtle A and then turtle B
4. Wait until they've "found" each other and one of them starts digging
5. Feed turtle C and attempt to feed the digging turtle a second time
   Notice there's love particles only on turtle C
   Notice that the digging turtle starts digging more rapidly regardless (and it takes longer)
6. Attempt to click the sea grass onto turtle C for the second time
   Notice turtle C doesn't accept the sea grass anymore eventhough it shouldn't have been able to mate

Expected behaviour

A turtle already in sand digging mode should not be targetable for breeding by additional turtles.

Actual behaviour

Although attempting to breed a turtle with one that is already pregnant doesn't seem to work, as it doesn't consume additional sea grass or show any love particles on the latter, it does actually match the two up with each other in some invisible way.

Also note

The result of this issue is what looks like bug MC-130871, however I can't tell if it is the same result of a different issue or just the same issue, considering that the description is very different.

Secondly, prior to the fix to turtle breeding in 22w44a, this "double pregnancy" used to cause an actual double egg laying. Upon laying the first batch of eggs, and reverting from pregnant model to normal again, (a few inconsistent seconds later) it would suddenly turn back to pregnant mode and start digging again. This doesn't seem to happen anymore, but the above behaviour seems to suggest there still is some kind of double pregnancy happening.