System not working when SDRAM Controller on Databus

I'm creating a system on Cyclone 10 with a RISC-V Processor from Vectorblox (orca-1) . The idea is to have a Bios on the onchip memory, which initialises a serial connection (UART). This serial connection should then be used to store the actual program into the SDRAM.

First I've made a system only with the onchip memory and the serial connection, which worked fine. The odd thing is, as soon as I add the SDRAM Controller, the system is not working anymore. If I remove the Controller from the data Bus, the systems is working again.

To me this doesn't really makes sense. Does anyone have an idea what could cause this problem?

I'm using Quartus 18.1.

The RGB_Array is a custom IP-Block I've made. As I thought this would might be a potential source of the problem, I've disconnected it. Anyway this was not helping.

Update:

I still can synthesize the whole system and download it. Anyhow it seems like the Bios is not executed. But it is hard to say at which point the system fails, since I have no possibility yet to debug the software. Currently I'm using the RGB_Array for displaying states, but all LEDs stay off.

Thanks in advance for your efforts!