Audio Track lost it's Send to Delay Plugin on Aux Track

[Wolfgang_2]

Hi to all,
I'm new to ProTools but not to Recording / Mixing at all.
After twelve years of working with Cubase VST 5 ( no need to upgrade )
I gave Pro Tools a shot.

Basically it's all ok, but I noticed an error for which I need help.
On my mixes I use automated Plugin mute / - unmute amongst others.
When jumping back and forth (on the fly ) during playback the connection of the send track to the Delay Plugin ( and only the Delay Plugin ) on the dedicated Aux Track get lost very often.

I can see the change of the color on the send icon of the source track during ' mute on / mute off ', but the corresponding Aux Track doesn't work.

The only way to get out of this is to change the send target from Delay to another send target like e,g, Chorus and then back to Delay.

Have I done anything wrong ?

I would like to post a screenshot of my Mix Window but I have no clue how to do.

I've updated to Version 9.02 a few days ago, but the error happens on both versions.

Regards
Wolfgang