Stale Beer?

I have been drinking San Miguel beers for a long time.  But after the alcohol ban was lifted, I tried several kinds of San Miguel from my local Metro supermarket.  Even one destroys my stomach the next day.  There does not appear to be any issue with the taste.  Other import beers don't do this.
Could this be an issue with the beer being in storage for a long time? 
I don't see a sell by date, there is just a 5 letter code.

On 6/14/20 we had 4 family members consume a dozen San Mig Lites in cans, there were no instances of gastric stress reported.

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