Those files are not there.

On a brighter note this has been good since the last couple of updates (0.13.14; 0.13.15 ?). No trace of visual defect. If it was intended fixed, thanks !

Thanks for the help;

I haven't tried deleting crop-cache.dat. I don't know what it is or where it is. Searching the factorio installation directory didn't locate one.
I also looked for a factorio-current log file in the installation directory - there isn't one.

With the latest update, 0.13.11, the problem is much less severe. There is still a discontinuity, but it is not really evident on joined-up pipes.

selecting start up options of --force-opengl, --force-d3d or nothing made no difference.

I'll post a log file if I can find it and a file upload ...

Thanks for the replies. I deleted the game files from my steam library, and did a cache refresh. Steam told me it was updating files, and re-downloaded everything.
I started up the game and loaded my last save. It looks just the same.
To be sure, I de-activated all mods (FARL, RSO, AyrAs Basic Kit ...

The pipe graphic appears displaced, leaving ugly gaps. It is particularly bad on North / south pipes-to-ground. The game plays normally, but the graphic is ugly and constantly reminds me that the game is broken. Has been present since 0.12. This screenshot is from the latest 0.13.10