I think there is an argument for simply saying falling climbers in your particular case, as it will be clear that all those on the climbing wall are using ropes. This refers to climbers falling off the wall and onto the rope (rather than onto the ground).

I presume your text continues Aufgrund der Gefahren durch ins Seil stürzende Kletterer und durch die Gefahr von herabfallenden Gegenstände

Learning to Climb Indoors - Eric J. Horst

Some toprope climbs will be easy; you'll breeze up the wall on your first try. Other routes might spit you off onto the rope - called a fall. (p. 6)

Glossary (p. 182)
Fall - disengaging the rock wall, intentionally or unintentionally, as in "falling onto the rope" or "falling off a boulder problem"
https://books.google.co.uk/books?id=SfK_UcWPHigC&printsec=fr...

On-demand lead climbing courses
You will be expected to let go of the wall and fall onto the rope when requested. If you feel scared while top roping, perhaps leading isn't for you.
http://hangdog.co.nz/lead-courses.html

The Indoor Climbing Manual - John White
Using a buddy to belay with – ideal if you're [a] backing up a beginner or for testing a short fall onto the rope (p. 77)
https://books.google.co.uk/books?id=9IB1BQAAQBAJ&printsec=fr...

Sport climbers climb for difficulty, not speed or height as some people think. We try to hold onto the smallest and worst grips at the steepest angles possible, and if we can get to the top of a route without falling (onto the rope for safety, of course), we’ve succeeded.
http://www.paleoplan.com/2011/08-19/athletes-and-paleo-a-cli...

Image
Ins Seil stürzende Kletterin. Foto: Marco Kost
https://www.jdav.de/schulungen/fortbildung/jugendleiter-fort...

This is also the solution adopted by the translator of this German-language text

Unser stärkstes Set wurde speziell für das Sportklettern entwickelt. Mit 1,1 Tonnen Karabiner-offen-Bruchlast und breiter Seilauflage lässt es sich seilschonend und ohne Hemmungen ins Seil stürzen.
Our strongest set, especially made for sport climbing. The 1.1 tons gate-open-breaking load and a large diameter allow rope friendly and fearless falling.
http://downloads.austrialpin.at/AUSTRIALPIN_Workbook_2018/PR...