rooted android device freezes when writing to /system

Question

I try to replace the build.prop in the system partition of my android device and it fezzes. I have rooted a samsung tablet sm-T850 with twrp_3.1.0-1_sm-t825_5417 and SR3-SuperSU-v2.82-SR3-20170813133244

the commands I have used to do this is :

gts3llte:/system # mount -o rw,remount /system

gts3llte:/ # mount -v | grep system

/dev/block/mmcblk0p44 on /system type ext4 (rw,seclabel,nosuid,noatime,norecovery)
gts3llte:/system # dd if=/sdcard/build.prop of=/system/build.prop

FREZZES!

device details:

• Galaxy Tab S3 (SM T825)
• Android 7 Linux version 3.18.31-11628211
• su version 2.82 also tried 2.79

Other symptoms:

• same happens with mv and cp

• I can create files in /system

• I can append text to /system/ build.prop

• if I reboot the tablet the new files are gone

• I have also tried with busybox’s mount and dd having the same results

Any ideas on whats wrong? Many thanks!