You have to release ctrl for every spell cast switch
Reproduce:
- Equip 2 runes with long cast times (like MM or cons)
- Hold ctrl
- Start casting 1, then press 2 while still holding ctrl
- It should start casting spell 2, but spell 1 continues to cast
In comparison, try:
- Press ctrl+1 to start casting 1
- Release ctrl
- Press ctrl+2 to start casting 2
- It switches casting as intended