I use the Bitcoin wallet by the Bitcoin Wallet Developers.
Wallet 9.03, Android 9, Huawei P10 Plus.
After trying to send bitcoin to my Coinbase account, the message "Bitcoin not sent" appears in my Bitcoin wallet, but the bitcoins are gone.
Neither have they arrived in my Coinbase wallet, so basically the bitcoins are just gone at this moment.
I have sent a "crash report" to email@example.com, but have not received a response. It's about 1 week since I've tried this.