The phrase "isolated incidents" means that something happened, but it happened only rarely or in a few specific cases. It suggests that the occurrence is not common or widespread. Full definition
These are not isolated incidents mind you this is an everyday occurrence. (joystikrevolution.com)
Within the last year, nightly news reports have informed the public of several isolated incidents of accidental food poisoning at some public schools. (articles.chicagotribune.com)
There are reports of longstanding fear and anticipation of abuse, followed by a «confirming» but isolated incident in which actual abuse took place. (parentalalienationsupport.com)