RuntimeError: memory access out of bounds when using exec multiple times in a row

**Describe the bug**
When repeatedly executing an ffmpeg operation (using `ffmpeg.exec`) either in a loop or manually by clicking a button, after few tens of operations (minimum was 15, maximum was 65 depending on the complexity) the worker dies with `RuntimeError: memory access out of bounds` error.

**To Reproduce**
Repeatedly call exec method of the same worker. Reproduced with all exec arguments I tried.

**Expected behavior**
Worker not dying and completing operations as needed.

**Desktop (please complete the following information):**
- OS: MacOS
- Browser chrome, safari

**Extra**

The problem does not happen with reloading the worker between execs.