**Cubase version:** 15.0.30.287
**OS:** macOS 26.6.2 (25G83), Apple Silicon (arm64)
**Steps to reproduce:**
1. Open Studio → MIDI Remote Manager
2. Click “+ Add Surface” and create a new custom MIDI Controller Surface (custom manufacturer/model name, any MIDI input port)
3. In the Surface Editor, click the back arrow (top left) to return to the MIDI Controller list
4. Cubase crashes immediately
**Crash details:**
EXC_BAD_ACCESS (SIGSEGV), KERN_INVALID_ADDRESS at 0x0 - null pointer dereference on the main thread, triggered during mouse-up event handling (_routeMouseUpEvent) inside Cubase’s own code (not a plugin or OS framework).
**Additional context:** Separately, the Assignment Assistant (“Zuweisungsassistent”) in the MIDI Remote editor did not detect any incoming MIDI at all - neither from a virtual CoreMIDI port nor from a real hardware controller (Novation Nocturn Keyboard) - before this crash occurred. Possibly related to the same instability in the MIDI Remote module.
Top frames of the crashed (main) thread from the .ips report:
```
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
Thread 0 Crashed:
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
0 Cubase 15
14 AppKit _routeMouseUpEvent
15 AppKit -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:]
16 AppKit -[NSWindow(NSEventRouting) sendEvent:]
17 AppKit -[NSApplication(NSEventRouting) sendEvent:]
18 AppKit -[NSApplication _handleEvent:]
19 AppKit -[NSApplication run]
```
Happy to attach the full .ips crash report if useful.