Indesign book document : hyperlinks to pages in other documents not working in pdf

I have an Indesign book document with 350 pages in 3 documents.

I have hyperlinks linking to pages in other documents (on the master page of each document).

They do not work in the exported interactive pdf. Links to the same document seem to work.

I examined 2 of these broken links in Acrobat - the result is attached.

How can I solve this problem? Thanx a lot.