VERY common. Our local hospital basically killed my FIL, MIL and mother due to repeated gross incompetence, over several years.
It took the GP surgery 2/3 years to realise my DH had cancer - he'd literally never been near the surgery for a decade or more and then suddenly started having lots of different medical problems, meaning maybe a dozen or two dozen GP appointments over 2/3 years where they just constantly fobbed him off. It simply never occurred to them that something serious may be happening when someone who had previously not gone near the surgery suddenly going almost every month for different things. It took a locum to take a proper look at the notes and what symptoms my DH told them he was suffering from to order a special blood test which showed he had a rare form of bone marrow cancer. When we got the official diagnosis and "googled" his symptoms, they were text book for his cancer.
MIL, otherwise fit and healthy, got double pneumonia and was blue lighted to hospital the day after a GP appointment where the GP told us her chest was "clear", that was after 3 other GP appointments over the month due to her worsening breathing. She languished in A&E for 48 hours on a trolley in a corridor being completely ignored - we had to feed her, water her and take her to the loo. On the third day, she was finally taken to x-ray and then put on a ward, she was eventually put on IV drips, but died before they could take effect.
FIL languished on a ward for weeks as different doctors came, ordered more tests, (many repeated ones that had already been done) and just fobbed him off for another doctor to try to work out the problem on the next round. He lost several stones in weight, contracted a couple of hospital acquired infections, and was barely able to sustain the operation when they finally decided what was wrong with him and what needed doing. He just about survived it, but a couple of years later was diagnosed with cancer, and was in and out of hospital, again, several hospital acquired infections, before they finally did the operation they said he needed a year earlier (for cancer!!!) - this time he wasn't fit enough by the time they finally operated and he died shortly after the op.
When my mother went in for a hip replacement, her diabetes went out of control and she went into a hypo twice. Despite the fact she was diabetic being on her admission notes, along with a note of the medication she was on, apparently the ward nurses hadn't given her any diabetic medication nor done any blood sugar checks throughout her stay on the ward.
It's no surprise that there is such a rise in medical negligence complaints/claims. A lot of the staff and management don't seem to have a clue what they're doing and other staff end up picking up the pieces and fire fighting.