What happens when HDMA triggers in the middle of an OAM DMA?

Does the HDMA manage to read the data? Does the OAM DMA continue during the HDMA copy? Etc.

No file, test, or entry point is mentioned. Start by researching Game Boy HDMA and OAM DMA timing and any existing Pan Docs sections covering either transfer; done means documenting the interaction and its timing clearly enough to answer each question in the issue.

Written by the indexing model from the issue text.