Crossbows uses the crossbow.loading.middle as the end sound instead of using crossbow.loading.end sound. To hear the sound you must use "/playsound crossbow.loading.end" and charge a crossbow.
Load a crossbow and the loading middle sound plays twice. One when charging and the other one as the loading end sound.
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Comments 1

Thank you for your report!
We're actually already tracking this issue at MCPE-53297, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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