Multi-select filter returns incorrect number of features when multiple values are selected

[RastoHu]

Description

When a multi-select filter is configured on an array-type text field (e.g. "Favorite cities") and the user selects multiple values (e.g. Vienna and Prague), the filtered feature list shows fewer results than expected. Features containing either of the selected values should all be returned.

Environment
[x] Staging [ ] PROD

Application (+ app version, build, operating system)

• Mergin Maps mobile 2026.3.0, Android 16 (Pixel 9)
• Mergin Maps mobile 2026.3.0, iOS 26.0

Steps to reproduce

1. Clone and open project tester-ws-1/test_feature_filtering in the mobile app
2. Open Filters → select filter Multi select-photo_survey-Favorite cities
3. Select values: Vienna and Prague
4. Tap Apply filters
5. Open the photo_survey features list

Actual results

2 features are shown.

Expected results

3 features are shown — all features whose "Favorite cities" field contains Vienna or Prague:

• Monica Geller — {Bratislava, Vienna}
• Chandler Bing — {Bratislava, Prague}
• Janice Hosenb... — {Budapest, Helsinki, Prague}

Screenshots or logs

QGIS attribute table confirming expected 3 matching features: (see attached)

Conclusion
Created by Claude and supervised by a human test analyst.