When using ExcelReader in a loop, an IllegalStateException occurs at random times.

Hi @locodust6, whilst I don’t know the cause of the problem, in cases where strange things happen on reading files, I would generally ask the following:

are the files that are being read:
(1) On the local drive of the machine where the workflow is running
(2) On a local network share
(3) Via a url (i.e. a web location)
(4) In a “cloud folder” on the local drive (such as onedrive, dropbox etc) where the file is being synchronised with a cloud service
(5) From Sharepoint
(6) Other?

For anything but option (1), there is always the possibility of some kind of latency occurring which causes problems and might only be apparent during some form of repetitive processing. As mentioned, this may not be the cause but it’s always worth exploring with a view to ruling this out.

(There is a difference in the underlying java software used for reading Excel in KNIME 4.7 and KNIME 5.x which has been apparent from another topic)

Another thought, what happens if you put a Wait node with a time delay of maybe 10 seconds (quite a long delay, just for testing!) immediately after the Excel Reader? Does it then work?