DDR3 cannot read data when burst length larger than 8, Maximum Avalon-MM burst length set as 1024

Hi everyone,
my work Environment : WIN10 64bits, Quartus II 18.1, modelsim-altera 10.5b, cyclone V E 5CEFA9F31I7N, Micron MT41J128M16JT-125*2.

Q1: I configured the Maximum Avalon-MM burst length=1024 of the avalon bus in the DDR3 IP Core. In the actual test, I found that if the read burst length is less than 8 (8 or 4), I can correctly write and Read the data(Fig1), but when the read burst length is greater than 8, the data cannot be read out(Fig2 write burstlength=16，read burstlength =8), in this case, I don't know whether the data is written to DDR3, why does this phenomenon occur? What are the possible reasons?

Attach the qar file.

Q2: I used two DDR3 chips, the number of chip selects should choose 1 or 2 ?(Fig3)

 Fig1

 Fig2

Fig3