These warning spam the console in Play mode for different particular projects:
Internal: JobTempAlloc has allocations that are more than 4 frames old - this is not allowed and likely a leak
To Debug, enable the define: TLA_DEBUG_STACK_LEAK in ThreadsafeLinearAllocator.cpp. This will output the call-stacks of the leaked allocations

To reproduce:
- download this project
- make sure the profiler window is open.
- go to: HexartUI->Scenes->Demo(Desktop)
- Run the scene: sometimes this will trigger the warning immediately
- if you don't see the issue, play through the UI a bit

Note: while i was investigating this issue, I also got a crash. See the Editor.log for stack trace (line 1935)

0x00007FF6B71EF0BE (Unity) memcpy_repmovs
0x00007FF6B4C966E0 (Unity) profiling::ThreadDeserializer::ParseBlock<0,0>
0x00007FF6B4CA2318 (Unity) profiling::ProfilerFrameDataDeserializer::ParseThreadJobFunc
0x00007FF6B5773038 (Unity) JobQueue::Exec
0x00007FF6B57794C8 (Unity) JobQueue::WaitForJobGroupID
0x00007FF6B5757138 (Unity) CompleteFenceInternal
0x00007FF6B4CA2761 (Unity) profiling::ProfilerFrameDataDeserializer::ReadData
0x00007FF6B4CA2E19 (Unity) profiling::ProfilerFrameDataDeserializer::ReadThreadFunc
0x00007FF6B5AC4097 (Unity) Thread::RunThreadWrapper
0x00007FF953013034 (KERNEL32) BaseThreadInitThunk

Reproducible on Windows only.
Reproducible on 2019.1.0b3 and 2019.2.0a4
Note: this only seems to repro on some of our Lenovo ThinkPad laptops, bu tnot on more powerful Desktop PCs.