What causes this error

Does anyone know what causes this error, when I try to create an asset

TransactionPool.Remember: txn dead: round 20245341 outside of 20243952--20244952\

it happens occasionally

The transaction has a first/last valid round, when it gets submitted the current round needs to be somewhere between the two.

In the example you posted the current round “20245341” is not between the first/last valid of “20243952”/“20244952”



can you say, what causes it?
A delay in submitting transactions?

Yes. A delayed transaction can cause that - but please note that were referring to a pretty long time here. I.e. in the order of hours.

Alternatively, you might have your transaction being created by a node that wasn’t caught up… which explains the large rounds gap.