Waiting list remaining spots decrease twice per converted signup

Every waiting-list signup that is later completed (payment link flow) is subtracted twice from the remaining-spots figure the visitor sees.

Environment: Eventin Free 4.1.21, WordPress 7.0.3, PHP 8.2, verified on a clean copy of the plugin (byte-identical to the wordpress.org zip).

Real numbers from my site (waitlist limit 25; three signups of 7 + 3 + 1 = 11 tickets, all converted and completed):

• The etn_global_waiting_list meta (and the admin panel) shows 14 — that is 25 − 11, discounted on completion.
• The event page capacity line shows “Waiting List: 3 spots available” — that is 14 − 11, discounted again.

Why it happens — two independent subtractions of the same signups:

1. On order completion, OrderTicket::order_status_completed() (core/Order/OrderTicket.php) persists etn_global_waiting_list = max(0, current − quantity) — a destructive write to the stored limit.
2. On render, the purchase widget computes remaining = max(meta − sum of waiting_list_count, 0), where waiting_list_count (core/event/Api/EventController.php → etn_get_waiting_list_counts_by_slug()) counts the same orders again.

Each side alone would be correct; together the same 11 tickets are removed twice (limit 25 → real remaining should be 14 → the visitor sees 3).

Related detail: etn_get_waiting_list_counts_by_slug() (utils/functions.php) counts orders flagged is_from_waiting_list with any status — cancelled or failed signups keep occupying spots forever, and trashed ones too.

Impact: the public waitlist counter drains at twice the real speed and never recovers, so events show a full waiting list long before they are.