I had a problem with sudden fuel issues in early 70s, in an Opel GT....car would die...start right up, and drive another 14 days , or shut down 5 minutes later..very frustrating ,esp in 5 oclock traffic in middle lane on a freeway overpass (hill)....eventually we found it.

the carb on a Opel GT had a male connection to a rubber fuel line that was pressed on over the enlarged end.
a prev owner had replaced the rubber line , cut it with a pair of pliers...the inside had a small piece that was probably partially loose when he installed it, when pushed on to the male connector , it severed, the little piece now loose by itself inside the rubber line....it would twirl inside the fuel line in the fuel stream, some times get right in front of the opening ,where it was too big to get in, shut the flow off..then you start up, it could cut flow off right away, or could twirl around in there , as it fit fine inside the rubber line, for minutes ,days or sometimes weeks.
But problem got solved...sometimes issues are caused by very tiny problems.