I contacted Shopify support and attached my screen record.
They resolved the issue one day later.
Now the POS app and extensions are working as normal.
Topic summary
Post-update performance and reliability problems with the Selly app on Shopify POS Pro. Multiple stores report severe lag and unresponsiveness after ~10 minutes when Selly tiles are active; removing Selly restores normal POS performance.
Symptoms and impact:
- Discounts created in Selly no longer stay toggled “on” in POS, breaking event promotions.
- Cart extensions (Selly, Smile, Infinite Options) stopped loading for one user.
Environments noted:
- iOS 16.4.1 with POS 8.9.0 (lag tied to Selly tiles).
- iPad Pro with POS 8.21 (cart extensions not loading).
Troubleshooting tried (no lasting fix):
- Updating POS/iOS, reinstalling Selly, factory reset, removing apps one-by-one. Removing Selly tiles is a temporary workaround for lag.
Outcome/updates:
- One case was resolved by Shopify Support within a day after submitting a screen recording; specific cause and fix were not disclosed.
Open items:
- Root cause of Selly-related lag and discount toggle failures remains unclear.
- Whether there’s an official fix or workaround beyond removing Selly.
- How to export loyalty points data from Selly.
Status: Partially resolved. Support-assisted fix helped one user; core Selly performance issue after the 8.5 update remains unresolved for others.