Problems with libQtOpenGL.so.4.8.7

[jjgiblin]

I've been working on modifications for several linux programs; working on Linux Mint 18.2.
A number of programs, including Okular, Octave and FreeCad, give me the same error when I try to run them. I haven't changed these programs at all, but I have added qt version 5 to my machine. The particular error in all three is:
symbol lookup error: /usr/lib/x86_64-linux-gnu/libQtOpenGL.so.4: undefined symbol: _ZNK14QWidgetPrivate17hasHeightForWidthEv
libQtOpenGL.so.4 is merely a symlink to libQtOpenGL.so.4.8.7, in the same folder.
I've checked both libraries with readelf -Ws and nm -D, and both commands show that symbol as present.
I also have Qt 4.4 and Qt5.5 in other directories, but these all have that symbol defined.
Any clues on how to resolve this?

[SGaist]

Hi and welcome to devnet,

How did you install both versions of Qt ?

[jjgiblin]

Qt4 was included with the Linux Mint 18.2 when I installed it. I added Qt5 by downloading qt-opensource-linux-x64 from the qt.io archive site. Not sure, but I think the problems began occurring after I installed Qt5

[SGaist]

And where does your Qt 4.4 come from ?

[jjgiblin]

also from the qt.io archive site

[SGaist]

Qt 4.8.7 being already outdated and having reached end of life, why are you using Qt 4.4 ?

[jjgiblin]

Why are all three versions now having this same problem, and why did this problem show up after I installed the latest stable version (at the time).?

[SGaist]

I don't know. What I would do is to remove all non-system versions you install and check if you still have that problem.