Multitouch with 3 buttons gets some of them stuck

[natewind]

Describe the bug

• On GBA, when I hold Left/Right + A and try holding R with the index finger without releasing A (e. g. using the Flying Armour soul in Aria of Sorrow), R doesn’t trigger, and instead A gets stuck until I press it again. This does not happen with Up/Down.
• The same happens if I press L instead of R: it shouldn’t do anything in this case, but instead A gets stuck.
• When I hold B instead of A, it’s still A that gets stuck.
• When I hold Left/Right + L (backdash in AoS) and try to jump/attack (A/B) during the backdash, A/B doesn’t trigger, but L gets stuck. This does not happen with R.
• When I hold L + Left/Right (in that order!) and press something on the right, Left/Right gets stuck. Based of this and the previous case, I think the last button gets ignored and the previous one gets stuck.
• When I hold A/B + Left/Right (in that order!) and press B/A, A/B + Left/Right get stuck together.

To Reproduce

1. Open a GBA game.
2. Hold Left/Right + A.
3. Press L or R.
4. Observe A getting stuck and L/R ignored.

Expected behavior

R or L triggers, nothing gets stuck.

Screenshots

Smartphone

• Device: Huawei P9 Lite
• OS: Android 7.0
• Browser: Vivaldi
• Version: 6.4.3171.134

Additional context

• Lemuroid version: 1.15.0 (Play Store)
• Is the browser relevant because Lemuroid is web-based? In that case, I also have an app called Android System WebView (119.0.6045.194) — maybe Lemuroid uses that instead? Or is it another part of the system, and they work together? When I open links in other apps, it says “Running in Vivaldi Browser”.