In a letter seen by The Morning Advertiser, C&C, which distributes through various wholesalers including Bibendum and Matthew Clark, warned businesses to expect “temporary changes to order and delivery days” between Thursday 26 January and Thursday 2 February.
According to the letter, the order cut off for final delivers on Friday 27 January was 12:30 on Thursday 26 January, with orders able to be placed again on Wednesday 1 February for deliveries on Thursday 2 February.
However, some firms are still unable to place delivery orders more than a week past the original deadline.
One operator, who wished to remain anonymous, said: "I placed orders [but] then they cancelled everyone's order because of problems with the system."
"They told us to reorder, but they still can't get a stock and they can't tell us when they're going to get stock."
"It's going to be a few weeks before it's all settled down. I’m running to shops to buy stock to fill gaps. It's not just me, I'm speaking to other operators who buy from them as well, we are all in the same boat."
"[We’re] wasting time running around buying stock, and then also you're trying to buy stock that's not commercial, it's not in every shop in the high street, it’s not great."
"It's a disaster for them, obviously, but it's a disaster for the rest of us when [we’ve] got all these other problems."
The source added while C&C had been good at keeping in touch with clients, the "stressful" situation had left many operators feeling like they were "panic buying".
Additionally, they stated many firms had struggled to open accounts with other wholesalers as they are already at capacity.
C&C Group managing director Andrea Pozzi said: "On Wednesday 1 February, as planned and communicated to our customers, we implemented a major operating system upgrade across our businesses in England and Wales [to] improve our service to customers, the same operating system that has been successfully implemented in Scotland."
"We are accepting and receiving all customer orders as usual however, processing orders is taking longer than we expected."
"This is a temporary situation which will be fully resolved shortly. We thank our customers for their support as we prioritise resuming our usual service levels. Customers in Scotland are not affected."