See screenshots:
{F25675816}
{F25675819}
The invisible text has width 1010px (first screenshot), while the syntaxhighlight has 1041.2px (second screenshot), so in the text the word "sein" wraps to the next line, while it is still visible in the first, causing everything that follows to fall out of sync, e.g. the cursor was at the end of the bluish area in the first screenshot while it should have been at the end of what's visible in the second screenshot.
This is probably caused by the `chimera` element (visible in first screenshot) at the start of the line, which has (at least in Firefox) a width of 2px.
Full text (if you want to try to reproduce, together with window.innerWidth === 1280):
```
== [[ETCS Stop Marker]] ==
ist keine Person --[[Benutzer:Eingangskontrolle|Eingangskontrolle]] ([[Benutzer Diskussion:Eingangskontrolle|Diskussion]]) 12:40, 5. Sep. 2018 (CEST)
:Falls du irgendeine nützliche Information übermitteln wolltest, ist sie bei mir nicht angekommen. Falls es ein Fehlerbericht sein sollte,
```
I have no real idea why the widths are not only different, but also differ that much, but it could be something with a scrollbar:
Toggling `overflow: auto !important;` on `.ve-init-mw-desktopArticleTarget .CodeMirror-scroll` does fix the issue, but causes a similar one in the line above instead.