Monday - last edited Tuesday
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As this behaviour only occurs in YouTube, there could be crash occurring within the app. Make sure it is fully up to date through the Play Store. After that, clear the cache and monitor. You can do this through Settings > Apps > YouTube > Storage > Clear Cache.
Failing that, try resetting the app entirely by clearing the data. Same steps, just select Clear Data instead of Clear Cache.
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Issues can occur with apps locally, and not necessarily wide spread across all devices. The steps provided are to eliminate any local issues with the app as you mentioned it occurs when using this app in particular.
Wednesday - last edited Wednesday