Several additions to the description :
* Script loads truncated with a leading hex code (e.g. 1abe9),, then the truncated part
Turned to nginx servicing with CGI php :
* No change in behaviour (this eliminates web server desease)
Conclusion : no web agent implication, no server implication. What remains ?
I started rebuilding a new code base with last 3.1.7+ and launched upgrade. The upgrader noticed some of my tables were still in Antelope (no idea how i could miss the format conversion before !). After compressing tables, the script loading errors stopped. The amd typical design errors are much better reported).
Maybe this stops the topic...