An increased number of orphaned blocks compared to other coins is normal in the Gulden system. Because after finding a block the miner must wait till a Witness has checked and approved the block. This takes more time than the coins that uses only PoW as an approval mechanism and in the meantime another miner can find the same block.
But if your miner produce, let say, more than 1 out of 5 orphans it’s maybe a problem in your system. For instance a clock that doesn’t exactly match with the rest of the world. Or a bad position in the network that cause extra time delays. So check your clock and restart the wallet so he can connect to other peers in the Gulden network. Also a very slow or bad internet connection can cause orphaning.
If you checked the checkbox “automatically mine at startup” You wil see at every startup minimal one orphan because the wallet does start mining even if it is not yet synchronised. Because the last block the wallet knows about is quite “old”, at that moment the wallet mines with a very low difficulty to find a block quickly.
If the blockchain is running normal this feels like stupid behaviour and could/should be avoided, because now we see all these orphan blocks.
However: a wallet that is not yet synchronised cannot yet know the state of the blockchain and therefor has to act on what it does know, and that is only it’s own copy of the blockchain.
There are several reasons why the wallet indeed should start mining with it’s understanding of the blockchain at the moment it starts up. Some of those have to do with possible planned or unplanned softforks that happened and others have to do with possible attack vectors.

This post is also available in: Dutch