MPU60xx SPI block read - AccX OK, AccY, AccZ wrong

I use the MPU60xx with I2C and SPI interface. When using the SPI interface it fails to read the ACC values XYZ from address 0x3B and a length of 6. The AccX value is OK, but the AccYZ values clamp at 255. When reading the same range from the I2C based device it works.
When reading the individual AccXYZ values as 2 byte values sequentially from the SPI device it also works. Furthermore it works when reading 7 bytes starting with the address prior to the start of the ACC values. Are you aware of such a behaviour on SPI? This behaviour is a bit strange! Is there anything special to be considered when using SPI? What I am wondering is that the Gyro values seem to be OK when reading them as a block of 6 bytes (GyroXYZ).

Thanks a lot in advance for your help.

Regards,
Tom