How many FB pages can you merge?

I heard that there is a limit to the number of Facebook pages you can merge: 4, no matter if you merge them at once or over a period of time.

But I can't find any reference to that on Facebook's help pages or anywhere else.

Can someone confirm this with a link or something?

I have merged 5 pages 1 year ago and I got a new bigger page. What happened is that there is still one page I would like to merge with this new page. The names and labels are the same, I deleted all location information, still, I can't merge them. It said something like - error: too many merged pages. Do you know a solution for that? I heard that a request to Facebook could change the problem, but I'm not sure about that.
you can learn more in our Help Center here: https://www.facebook.com/help/249601088403018/?ref=u2u