No Waveform or Regions on few Tracks

i recently upgraded fron N4 to N7 and have few Problems :

When opening older N4 Projects on few (not all) Audio tracks i cant see any regions
or waveforms on the tracks , just transparent Shadows , i can hear the regions and metering Shows also
Modulation , but no visible regions with waveform… on other tracks it works fine in the same Project.

any hidden Setting or a bug?

btw saving as N7 session and reopen doesnt help

System Macpro 8core , 24 gb Ram , os yosemite , Motu ultralite

after spending few dozend euros on the (paid) steinberg tech telefon hotline , where i was told , due to incompatibilities
between N4 (from where i upgraded to N7) i had to open and save any PRE N5 project in N5.5 and open then that N5.5
project without hassle in N7… So … i have few hundred pre N5 projects it looks like lot of work and is a PITA…
at least opening PRE N5 projects in N5.5 worked .( after dowmload and install N5)

BUT opening theese N5 projects doesnt cure the problems , opening now some of them in N7 results in NO WAVEFORM
and transparent Regions ON ALL TRACKS .
( Global settings in N7 are on “Default” and other projects work fine)
All theese Tracks play audio fine , just NO VISIBLE WAVEFORM . Impossible to edit here anything ,
btw doubleclick on the regions opens the audioeditor and shows the waveforms.

is there maybe anywhere a waveform cache which could be deleted to force n7 to rebuild the waveforms?

no way i pay again for this sort of tech support , sorry , for this sort of bugs there should be FREE support.

MacPro 4.1 8-core 24GB , Yosemite , Motu Ultralite/ SPL Crimson , N5.5 latest , N7

is there maybe anywhere a waveform cache which could be deleted to force n7 to rebuild the waveforms?

Yes, from within the Project folder (with the project closed) simply delete everything in the Images folder. When you reopen the project it will rebuild those images.
I should also add that you can selectively delete files in the Images folder, too, if your track labeling is such that you know what everything is and only need to rebuild a few items. Likely a quicker method on larger projects, although the image rebuild goes pretty quickly overall.

so far i see all sorted out…
no problems with the waveform cache

when i choose for theese tracks with transparent events a color (upper menue) all waveforms are again visible…
it seems track color settings (or transparency) are not properly imported from earlier versions and
are often set inactiv , which results in transparent events without waveform on few or all tracks,

Since i was under the impression the visibility of waveforms and transparency of events is a Global setting ,not by track ,
(at least in earlier nuendo versions it is this way) i was a bit baffled.
i cannot see any rule on this : stereo , mono , interleaved , split … always audio tracks ,
sometimes all tracks in a session , sometimes only few , all sessions from N2 , N4 and N5.6 .

a mac only problem maybe?

Macpro 4.1 8-core , 24 gb , Yosemite , Motu Ultralite/SPL Crimson/AVID HD , PTHD12 , N7 , Artist Mix