One line in the Submissions Guidelines - "We pay royalties—a percentage of sales after production costs—on a quarterly basis" is worrisome. Royalties usually come off the top, period. Not off "production costs" which might be a way of hiding costs the author doesn't expect to pay for - editing, cover, formatting, ISBN, etc. Authors should not have to pay for these types of items unless that's clearly spelled out in the contract. This is a vague term that sends up a red flag for me, despite them including an equally vague definition in their FAQ section.
Publishers usually speak of net royalties, and these are usually paid for sales from third party sales. For example, at digital first publishers like Evernight and Siren-BookStrand, royalty rates are slightly higher for sales from their websites as opposed to third party sites like Amazon, because the publisher has a cost to list those books on those sites. The royalty rates are a bit lower on those sites, but that lower percentage is clearly spelled out as being based on the sales minus the cost to the publisher.
I'd clarify "production costs" in detail before signing a contract with Oghma. They include this question in their FAQ, but it's still worrisome to me because I've seen this type of thing before. I've seen publishers hide costs this way. If it's clearly spelled out in the contract, that's one thing, but I'd ask first. For example, I'm with digital first publishers, who typically do not send every book to print, yet I do not pay any of the printing costs for my books that do go to print. Those costs can vary widely, and that would cause some nasty surprises for the author come royalty time. Any costs an author is expected to pay for, especially any that are going to come off their royalties, should be clearly spelled out and detailed. Those costs can fluctuate, so the author needs to be made aware of that, and needs to be made aware of what those fluctuations might be from quarter to quarter.
There are references to imprints on their site not listed anywhere. The catalog of releases is for 2017-2018. They don't have many authors, but they do seem to be fairly new still. There are some editorial mistakes in the content, and some of it clearly hasn't been updated in a while. I'm always wary of publishing sites that don't proofread their content, or whose websites don't appear fresh or kept up to date.
I'd try looking for books by the authors on third party sites like Amazon. Read the reviews, looking for issues with editing especially. Look at sales rankings, especially for the newer books. You might also try searching for author blogs or social media profiles, to get an idea of how the authors are talking about working with this publisher. If an author is enjoying working with a publisher, they aren't shy about saying so, or about promoting other authors in the house. If the opposite is true, they are usually letting other authors know to steer clear.
Also, just as an FYI, this forum is searchable on the Internet, so it's possible the publisher could find this thread. But I haven't moved this thread to The Back Room because the original poster does not have access to post in that forum as a Basic member.