* In the early 2000s, they added support for Windows NT to the product. Unfortunately, they did this with an MPE compatibility layer that means the entire thing still thinks it's running on an HP 3000, so controlling it programatically means writing MPE job streams.
* It was originally written to store data in COBOL records. When they added support for SQL databases, they apparently just copy-pasted the schema verbatim from the COBOL copybook format. This means the database has no foreign keys, FLAGS columns all over the place (including tables where you have to JOIN ON SUBSTRING), and, most egregiously, a table with ITEMNO_001, ITEMNO_002, ITEMNO_003, PRICE_001, PRICE_002, PRICE_003 and so on, which has to be queried three times and UNIONed to get the data out.
* Printing packing lists requires not only a specific model of printer, but also an extra several-hundred-dollar chip to be installed in that printer. I'm told that this chip's sole function is to enable barcode printing.
I have no insight into what goes on inside the company that makes this thing, but it certainly looks to me like they have a severe case of technical debt. Any bug fixes generally take 4-6 weeks in the best case scenario, and frequently either don't fix the bug or introduce new ones instead. Their only customers are the ones that have been using the system for so long that they're stuck with the system, and can't switch--in fact, many of them are still running HP 3000 systems, which HP has been trying to end-of-life since at least 2006.
The end result of this is that the product is dying a slow, agonizing death of attrition. I think the only reason it still exists at all is because the company that makes it is stuck with support contracts that haven't expired yet.