[Will Chen]

Scenario: At stall 7, a defender erroneously calls and signals pick. At stall 8, thrower finally hears and acknowledges pick call and play fully stops. What should the stall count resume at?

In this scenario, since the thrower never threw the disc, “the opposition” retains possession, so 15.9.1 applies (and, more importantly, 15.9.2 does not apply). But 15.9.1 simply says “any subsequent play stands”, which, in my interpretation, produces the outcome of the stall count resuming at 8 (or at 6 if you want to add 9.5.4 into the discussion). I’d have guessed we’d want the stall count to resume at 1.

15.9.1. if the opposition gains or retains possession, any subsequent play stands.

15.9.2. if the opposition does not gain or retain possession, the disc must be returned to the last non-disputed thrower, unless 16.3 applies. The stall count resumes as if an accepted breach has been caused by the player who initiated the stoppage incorrectly.

[Will Chen]

Clarification: by erroneous pick call, I mean they echoed a non-existent pick call. (ie: not a retracted pick call)

[Meret Trapp]

I would understand it as follows:

15.9.1. and 15.9.2. clarify what happens if the disc has changed hands between the incorrect initiation of the stoppage and the actual stoppage of play.

The subsequent stall count should be determined by 9.5. regardless. Otherwise, the defence could gain a net benefit by calling incorrectly.

[Meret Trapp]

That would be indicated by the use of the words “retain” and “any subsequent play”.

[Rueben Berg]

“Scenario: At stall 7, a defender erroneously calls and signals pick. At stall 8, thrower finally hears and acknowledges pick call and play fully stops. What should the stall count resume at?”

It should be 1.
We will amend the rules accordingly.