This is an appeal to the maintainers of late Reg Plus, now Pie Register.
As you can tell this is a very much used plugin as it is a very useful and fully featured one. A great plugin from a user standpoint.
However, it seems that from the developer standpoint it is full of flaws.
Searching on the WP forums, people report a wide range of issues on a wide range of wp installation versions. I am just guessing this is due to the bad interaction that the plugin has with other plugins.
On my side I see some improvement compared to Reg Plus, but the same main error stay (suddenly and for no apparent reason the whole settings disappear and I have to reset everything from anew. At times it even causes bad errors in the DB so that I have to go in and repair them).
This has become a heavy maintenance and even potentially dangerous plugin. So before any further feature development I ask the maintainers to provide a stable version for the current plugin.