Not quite what you're asking as I'm the son, rather than the Mum, but largely me and my Mum had a fantastic relationship, as did my brother.
Usually we'd see each other at least once a week, and be on the phone once or twice more. My brother lived further away, (3 hour drive and a ferry ride) but they'd speak probably twice a week, and there were probably an average of 6 trips to see each other per year.
It helped massively that Mum got on well with both DP and my brothers wife. It's a lot easier when your partner actively wants to spend time with your family (DP generally preferred my Mum to her own family!)
The only times me and Mum tended to argue were when she'd get over involved or forget that we were fully capable adults in our own right. A couple of examples:
Our washing machine broke. Mum popped into our house while we were at work, measured up, and promptly ordered a new washing machine, and paid for it. An absolutely lovely gesture, but it meant that we suddenly had this appliance in our house that wasn't what we'd have ordered. I thanked Mum, but asked her not to do anything like that again, and she got the hump a bit.
Another example, we all went on holiday to Disney for a fortnight. Mum had the habit of second guessing our parenting decisions. Usually a mild irritation, but two weeks of "Won't DD be warm wearing that", or "Does she need a cookie, she won't eat her lunch" properly tipped me over the edge. We had a proper blow out, but we'd made up by dinner.
Most of the time, when I see friends who don't have a close relationship with their parents, it's because the stuff like the above is constant. They seem like they don't see their kids as proper adults, or almost like they're in competition with their kids partner for attention. My Mum had her moments, but by and large knew where the boundaries were.