Lately, I fly float planes almost exclusively in southern Alaska. (I highly recommend Return to Misty Moorings for that.)
I have seen this once with the Kodiak. Starting C&D in Juneau Harbor. Drifted close to shore, but when free and once in deeper water, could not get past maybe 30 kias and so could not take off. Something got into a weird state and there was no fixing it. I recently started using a pushback tool for holding float planes in one position. I think that may have been the issue - it really never let go.
I fly the Beaver mostly. It has an anchor feature which is useful. I’ll try the Kodiak again with and without the pushback tool. It’s probably a conflict of some sort.