Steps to repro:
1. Pull the Sponza URP project from here: https://ono.unity3d.com/test-data/gi-tests/SponzaLWRP and sync to revision 1ba7fdd9f457acff81428824ec6f3460e3e72ab4;
2. Open SponzaLightingDay scene;
3. Pull the Sponza scene to the Hierarchy;
4. Make sure that the scene is selected as a master scene, if not, double-click on SponzaLightingDay scene in the Hierarchy;
5. Make sure that GPU Lightmapper is selected as a baking backend for the SponzaLightingDay scene;
6. In the Lighting window press Generate Lighting button;
7. Once the ETA for the bake is visible, press Force Stop button in the Lighting window;
8. In the Lighting window press Generate Lighting button.

Expected result:
Baking with GPU PLM proceeds and finishes as expected.

Actual result:
Errors:
OpenCL Error: 'clGetEventInfo(event, CL_EVENT_COMMAND_EXECUTION_STATUS, sizeof(eventExecutionStatus), &eventExecutionStatus, NULL)' returned -9999 (CL_UNKNOWN_ERROR)!
OpenCL Error. Falling back to CPU lightmapper. Error callback from context: CL_UNKNOWN_ERROR

are shown.
Lightmapper falls back to CPU PLM.

Notes:
- Reproducible in Version 2020.2.0b3, 2020.1.6f1;
- Not reproducible in 2019.4.11f1, as the Force Stop button wasn't available in that version for the GPU Lightmapper;
- Reproducible on Windows 10 with NVIDIA GeForce RTX 2080 GPU.