troublesome
adj.causing a lot of problems, worry, or extra work. You use this to describe something that is difficult to deal with over a long time.
adj.causing difficulty, annoyance, or persistent problems. Often used to describe recurring issues or behavior that requires constant attention.
“The old car is becoming very troublesome to maintain.”
“The manager spent the afternoon dealing with a troublesome software bug that kept crashing the system.”
“While the initial symptoms were mild, the patient soon developed a troublesome cough that resisted standard treatments and required a specialist's intervention.”
Typically used attributively before a noun or predicatively after linking verbs like 'become' or 'prove'.
From trouble + -some.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.