Greetings Seb_ghe,
You've completed some great troubleshooting steps so far. To clarify, does the issue only occur with other apps as well? If so, these are some additional steps that may help resolve the issue:
"1. Remove all screen protectors, films, or cases from your device.
2. Check the speaker opening to see if it's blocked or dirty. On iPhone only, make sure that the receiver isn't blocked or dirty.
3. If necessary, clean the speaker or receiver opening with a small, soft-bristled brush. Make sure that the brush is clean and dry.
4. Go to Settings > Sounds (or Settings > Sounds & Haptics), and drag the Ringer and Alerts slider back and forth a few times. If you don't hear any sound, or if your speaker button on the Ringer and Alerts slider is dimmed, your speaker might need service.
5. If you hear sound, try making a call with your iPhone and turn on speakerphone. On iPad or iPod touch, make a FaceTime call. If you still can't hear, or hear static or crackling, then your network or reception could be the issue. Try to call again later, or from a different location."
More details here: If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker
If this issue only occurs in third party apps, the following steps can help correct an issue when an app is not working as expected:
"1. Close and reopen the app
Force the app to close. Then open the app to see if it works as expected.
2. Restart your device
Restart your iPhone or restart your iPad. Then open the app to see if it works as expected.
3. Delete the app, then redownload it
Delete the app. When you do this, you might lose data that was stored in the app. Then redownload the app. Then check to see if the problem with the app is fixed."
More details here: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open
If the issue only occurs with third party apps, we suggest that you reach out to the developer directly. You can follow this link to connect with them: How to contact an app developer
We hope this helps.
