First time reading this thread… but I can report similar experience with Mercedes Loughton Branch in London.
Ordered card in November and was advised delivery for March 2020, country then went into lockdown so I assume that car would be ready once business resumed, only to receive email from sales person advising that order was deleted by mistake at their factory in Germany and now they would have to re-order with new delivery for Sep 2020 (almost a year since order date Nov 2019).
First time with Mercedes and I have to say it feels like poor customer service and lack of putting customer first I finding solution.