What does "Let me know if the problem persists" exactly mean? [duplicate]
Solution 1:
Ambiguous.
In informal writing, "if" and "whether" are used interchangeably.¹ This is not recommended because it creates ambiguity, but it is an unfortunate fact. Consequently, the statement can mean either:
Let me know whether the problem persists.
or:
Let me know (only) if the problem persists.
Solution 2:
A logician might say that the person being addressed need say anything only if the problem did persist. In practice, the context will usually make it clear what is required.