Clicks at the start of a rendered file

Today I experienced a weird situation on Wavelab Pro 10.
I was mastering a 11 track record and when I got to track 6, every time I tried to render it there were some clicks at the beginning of it. At first I thought that it might be just a playback issue, but it wasn’t. The clicks stayed in the rendered file. I didn’t have any issues on the other tracks and the plugins used were the same, all of them inserted on the clip.
I tried to remove some plugins, but the only way to stop those clicks was to remove the external effects insert, where my analog chain is. Of course that wasn’t a solution.
Maximizing the waveform I could see that the clicks were audio interruptions. If I edit the rendered file and cut the 2 or 3 bits of silence, I get a perfect rendered file.
I changed several times the buffer size for my Lynx Hilo but that didn’t solve it.
Any help would be appreciated.

Is it something new? I mean, did you use the external effect before, without this problem?
Also, where is it inserted in WaveLab?

Can this be related to “the Playback Fade in” ?
File > Preferences > Audio Connections >
Playback tab “Options”
“Playback Short Fade in When Starting Playback”

regards S-EH

Thanks PG for your answer.
Randomly this issue has occurred since Last December when I converted myself to wavelab after 28 years of being a Protools user.
Every time this happens I can figure that it has something to do with the external effects insert. I forgot to tell you that it never happens in normal playback, just when I’m rendering.
Maybe I’ll just have to change my workflow inside wavelab and use a reference track to feed a recording track with my AD/DA to get the process more stable.

Thanks S-EH for your help.
I’ve never used the playback fade in. But today I checked that box just to see what could happen and it’s still the same.
Thanks once again
All the best!