Which Minimserver-Version for QNAP251?

[Klaus57]

I have a new QNAP 251.
Yesterday I installed Minimserver for X64 on QNAP -it seemed to be ok, I could see the Minimserver with minimwatch and configure it. Today I started the NAS -and I got the message from the NAS-IOS that I am using an uncorrect Minimserver-Version. The CPU run to 100%. So I installed the X84 Version - now I have the situation, that Minimwatch does not "see" the minimserver on the QNAP-NAS.
IOS-Version on the NAS is QTS 4.3.2
The HS251 has an Intel Celeron CPU J1800;

At the same time I use the QNAP HS210 - Minim Server works with this NAS without any problems.
So first of all: which Minimserver for the QNAP 251 is really correct?

Thanks for your advice,
Klaus L.