Hi!
My tower has 4 bands (20,1,3,7) and 1-7 beaming 4x4 MIMO.
I notice, that looks like 4x4 MIMO don’t work as soon CA takes place.

if i remove CA (by forcing to use only 1 band) then 4x4 MIMO kicks and i see something like this: My system:
Is this some expected behaviour?

Which is primary band in case of CA enabled? I'm guessing that +QRSRP only prints signal levels for primary cell and not the rest. Depending on your MNO config it might be one of lower-frequency cells which is primary - band 20 is 800MHz and so far I didn't hear of operator which would support 4x4 on that band. Band 3 is 1800MHz and can realistically support 4x4, antennae are often shared with band 1 (2100MHz). Band 7 antennae (2600MHz) can be considerably smaller than for B1 or B3 while having same gain, so this makes 4x4 easier to implement.

@mkx I know that +QRSRP prints only primary, and I am for sure now that my tower have 4x4 for 1,3 and 7. And I know, that 20 do not support (or rather no one do 4x4). All my test was made on 1 , 3 and 7 as primary (by locking that with … ="at+qnwlock=\"common/4g\....) and then after separately locking + "disabling" CA.
That test in my previous post was based on primary band 1 with and then without CA.
On side note, in my case, i am usually in 7 or 1 as primary. Never goes 20.
So, i am leaning to the MT bug or 4x4 don’t make sense in ATL LTE18 since i barely see where someone would have alone one of high bands.

Ok, case can be closed, thanks to MT suppoert. They did point out to read more cerefuly Quectel_EG18_Series_CA_Feature_V1.2 spec. 4x4 not works on all posible comubinatioins, more specifcaly, if you have more then 3 bands on tower, 4x4 will not work. Made tests - works according to spec.