My feeling is this was caused by COVID damaging the neurons or receptors of the stomach or duodenum, or, more likely that COVID caused a Magnesium Deficiency:

https://pmc.ncbi.nlm.nih.gov/articles/PMC10445067/

But some thoughts:

If the stomach is not emptying it means it is not getting the signal to empty.

Some of his symptoms signal high serotonin (panic attack, nasuea)

https://www.nature.com/articles/1300880

Anti-nasuea meds block the serotonin HT3 Receptor.

https://www.ncbi.nlm.nih.gov/books/NBK513318/

But the lack of gastric emptying is mostly controlled by high Cholecystokinin (https://www.uniprot.org/uniprotkb/P06307/entry)

https://pubmed.ncbi.nlm.nih.gov/645853/

Now it could be that his Cholecystokinin receptors are not getting this signal from the Cholecystokinin, or, since these are G Protein Coupled Receptors, that there is not enough GTP in the cell to create the cAMP needed for the stimulation to carry on down stream.

https://www.nature.com/scitable/content/ne0000/ne0000/ne0000...

To make GTP you need magnesium:

https://pmc.ncbi.nlm.nih.gov/articles/PMC3400779/

Magnesium is one nutrient found deficient in Gastroparisis:

https://pubmed.ncbi.nlm.nih.gov/2012043/

Not to mention that low magnesium is linked to worse COVID outcome.

Also, he said he had some tardive dyskinesia from some meds which would also point to low magnesium since low magnesium is linked to the disorder:

https://pubmed.ncbi.nlm.nih.gov/27816557/

Why did the ginger help? That is easy:

It triggers cholecystokinin signaling by activating the TRPV1. So more spicy foods will probably help as well. BUT, this to me would not be a long term solution since IMHO it would lower magnesium even more.

https://pmc.ncbi.nlm.nih.gov/articles/PMC11192538/

EGCG in green tea also triggers this receptor.

So it may be that he has some genetic issue with his Cholecystokinin receptor genetics that made him more vulnerable to a magnesium deficiency caused by COVID.

https://www.scirp.org/journal/paperinformation?paperid=11741...