I have yet to find a solid replacement for "Voice Memos" of iOS 5 & 6.
The newer "Voice Memos", even of iOS 12, is just horrific. The UX is terrible with very little feedback of what's going on, paused time at the top during background recording (but it seems to still be going), disappearing recordings and recordings just stopping unexpectedly - coming back to device with no audio after thinking it had been running for an hour.
I've tried a couple apps. One particular app called "VoiceRecorder" seemed to be most promising to me, but it doesn't seem to always record when the device is locked (it seems to go off after an undetermined certain amount of time).
Anyone know of a particularly spectacular audio recorder for iOS?