All due respect, but increased A/R is absolutely NOT a red flag. In fact, it's about as green as it gets. It means 3-1/2 times the sales.
Not sure how much you know about payment terms in Europe, but they typically run from 60 to 90 days. At 60 days, it means there have been at least $7M in sales per month.
Decreased A/R, on the other hand, would be a red flag. It would mean either decreased sales or that the company is so cash-strapped that they have begun factoring their receivables.