The chief executive officer took to social media on Thursday to scold Ionity GmbH, the charging venture part-owned by VW, over a regrettable experience driving an ID.3 to a summer destination. Diess said he had trouble finding a working plug along the Brenner Pass that links Austria to Italy.

“So I kept driving to Trento,” Diess posted on LinkedIn, before describing the Ionity charging point he found in the north Italian city. “No bathroom, no coffee, an out-of-service/broken charging point, a sad state of affairs. It was anything but a premium charging experience, IONITY!”

The venture set up by VW, Daimler AG, BMW AG and Ford Motor Co. in 2016 has been billed as established automakers’ answer to Tesla Inc.’s Supercharger network. But Diess’s criticism marks just the latest barb from one of its shareholders.

Silke Bagschick, head of marketing at the VW brand, last year said Ionity’s charging prices were too high. Audi boss Markus Duesmann told Handelsblatt newspaper in January that Audi was considering setting up its own charging infrastructure in big cities.

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The discontent with Ionity reflects German automakers’ view that charging infrastructure remains a weak link in their efforts to catch up with Tesla. After EV sales tripled in Europe last year, the companies fear long lines at charging points could put off potential buyers.

Ionity boss Michael Hajesch said in an interview earlier this year the venture was in talks with shareholders to substantially expand its European charging network to keep pace with rising sales.

An Ionity spokeswoman wasn’t immediately available for comment on Diess’s LinkedIn post.