This is a translation-length defect in the French base app, not something in your setup. "Compte du grand livre" is 21 characters and something in that code path is holding the caption in a 20-character field. Nothing you change in Sales & Receivables Setup or on the page will move it.
Two things are worth establishing before you escalate, because they decide whether this gets triaged as page-specific or as a base-app bug:
- Does it also fail on the standard Sales Order Subform and the Sales Quote Subform, or only on the Blanket Sales Order Subform? If only the blanket subform, the fault is in that page. If everywhere, it's in how the enum caption is being handled.
- Does it fail when displaying an existing G/L Account line, or only when selecting the type? You've described both, which is the worse case — if French users can't open a blanket order that already has such a line on it, say so explicitly. That changes the severity.
For the call stack you don't need anything clever: reproduce the error and use "Copy details to clipboard" on the error dialog. That gives you the AL call stack plus the session and correlation IDs, and it's the first thing a support engineer will ask for. Two caveats — the stack can come back trimmed when the failing object is Microsoft-published and protected, and what you see depends on your permissions, so try it as SUPER before concluding it isn't there. If it's redacted, fall back to snapshot debugging against a sandbox restored from Production on 28.3.
If the environment is wired to Application Insights, the same failure is logged there with its call stack, usually easier to read than the dialog and with an exact timestamp you can quote.
Route it through your partner as a support incident with that stack attached. If the failing object sits in the open-sourced base app, a GitHub issue tends to get triaged faster.
I don't have a page-level workaround for you. If it breaks on display too, the only interim option is having those users switch My Settings to English while working blanket orders until the fix lands.
