Hi Hank.
I have had similar experience although not with PBNs, but rather Web 2.0 and other "SEO Packages" offered here in BHW. In my personal opinion you are suffering from a Google Dance. Every webpage goes through this procedure, some webpages (Depending on the age of the Page * Not Site *) will see little to no dancing due to the Authority and Trust the page has already gathered in Googles Eyes. Results are never instant however and will take a minimum of 3 - 7 days, on average 14 days and for sites with little to no Trust / Authority will take 1 month + for a new webpage to finish the Google Dancing Process. This Google Dance proceedure is basically Google's Algorithm deciding on were best to place your website in the current SERP Results. Many factors will be taken in consideration and it's not all about the "Power" of a PBN but rather many other factors, in-fact there are over 210+ known currently in 2017 according to top SEO Professionals.
You should also NEVER remove a link once built unless it's 100% causing a Google Penalty, I.E Manual Spam Action or Penguin Algo Penalty, to learn more about this subject simply search on YouTube for these terms. If you are hit with Algo then you should first check to see if it's caused by Over-Optimization such as Keyword Anchor Text. You should aim for 3% - 5% being Money Keywords and everything else being Brand, Partial Match & Generic. For Example if you have 100 Unique Backlinks (1 Per Link Per Root Domain) you should aim to have no more than 5 of these links being your Money Keywords. From here you can build more "Power Links" such as PBN's and add 1 at a time (Wait 2 weeks for results) and keep adding until either your Reach No.1 position for that Keyword or you go down the ranking after 1 month waiting after placing the link (This is to make 100% sure it's not a Dance). If this is the case then you should simply go and add 20x Brand, Partial Match & Generic links in order to re-balance. Simply Rinse & Repeat.
Remember, Off-Page is roughly only 30% of SEO (Again according to Top SEO Professionals General Consensus) and 70% is all to do with On-Page, and when I say on-page I don't mean just Title, Description, H1, H2, H3, Paragraph & Images, this is just part of On_Page and you should (if you don't already know it all) go and do your research on google & youtube. The majority of on-page issues are caused by "Thin Content". This essentially means that Google does not like the information you have provided due to the size and scope of the article or page. You need to Research a subject matter, then write a full article all about it, in your own words and 100% unique (No copying). Aim to have your articles a bare minimum of 1000 words, stay away from those 300 - 500 articles as they are no good for Money Sites / Pages. I personally would invest a content writer to write maybe 3K to 5K words ($20 - $30 per article for average quality writer).
I hope this helps you.
P.S I do not offer services here on BHW, I am not affiliated with any services either. I simply found your post today and thought I could add value to this topic to give you my own personal opinion, of which everything I have written is my own personal thoughts and not "Official" or "Fact". I am just like you, still learning from the true professionals on the internet, Master Mind Courses & YouTube etc. Everything I have writen above is either what I have been told myself from people who know their Craft or they are the results of testing on many of my own Websites / Pages.
I wish you luck and have a great day.