Apple has released the seventh beta of iOS 12.4 to the developers

Release Notes:

Instruments
Resolved Issues
Resolved an issue where running an app in iOS 12.2 or later under the Leaks instrument resulted in random numbers of false-positive leaks for every leak check after the first one in a given run. You might still encounter this issue in Simulator, or in macOS apps when using Instruments from Xcode 10.2 and later. (48549361)

  iOS 12.4 Beta 7 released