DDR3 Memory errors but passes Calibration

you know.... these errors after calibration really grabs my attention... today i was messing with the UniPHY; and watch what i have observed:

i have written some value 5 in DDR address 0. then value 6 in DDR address 1. after some issues i restarted the controller; by glbal reset. and when i accessed same DDR addresses i'v downloaded something like 145121623 from address 0 and still 6 from address 1. and then it hit me.... whenever you reset that controller by global reset; it starts recalibration process. which is, (if i understand it correctly) it must send random values into the DDR into random addresses, and then downloads them back (similar to echo) and tries to determine timing margins. so exactly that phenomenon overwrited my value 5 at address 0. that is why documentation strongly recommends to reset the system by soft reset. not the hard one. since the recalibration process will overwrite some addresses in the DDR. ...well, that might be the reason...... or maybe these erroneous words managed to sneak at these addresses by some other way....? what do you think???