Syncing takes increasingly longer on Dendrite

### Steps to reproduce

1. Sign into Element
2. Wait a few days as you're messaging as normal
3. Syncing progressively takes longer and longer to complete

### Outcome

#### What did you expect?
I expected syncing to be fast and take the same amount of time as it did initially. Currently however I need to occasionally sign out and back in for it to fix itself.

#### What happened instead?
Syncing takes longer the more I use Element. It gets to the point where I'm just waiting on the chats screen for 30 seconds each time I open it. This doesn't happen on Element X's sliding sync on the same instance (self-hosted).

### Your phone model

iPhone 12

### Operating system version

iOS 17 Beta 3

### Application version

Element 1.10.14

### Homeserver

Dendrite 0.13.1

### Will you send logs?

No