I am in search of solution to this problem. 
Looking at the logs, I found the following information. 
When I try to create a folder, I view it in the Samba log:
[2016/11/04 14:56:05.180028,  3] ../source3/smbd/vfs.c:1214(check_reduced_name) 
check_reduced_name: couldn't get realpath for New Folder 
[2016/11/04 14:56:05.180054,  3]
../source3/smbd/filename.c:1426(filename_convert_internal)
filename_convert_internal: check_name failed for name New Folder with
NT_STATUS_UNSUCCESSFUL
[2016/11/04 14:56:05.180073,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_UNSUCCESSFUL] || at ../source3/smbd/smb2_create.c:293
[2016/11/04 14:56:05.180939,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:56:05.182362,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:56:05.182550,  3] ../source3/smbd/vfs.c:1214(check_reduced_name) 
check_reduced_name: couldn't get realpath for New Folder 
[2016/11/04 14:56:05.182575,  3]
../source3/smbd/filename.c:1426(filename_convert_internal)
filename_convert_internal: check_name failed for name New Folder with
NT_STATUS_UNSUCCESSFUL
[2016/11/04 14:56:05.182593,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_UNSUCCESSFUL] || at ../source3/smbd/smb2_create.c:293
When I tried to rename the file to owncloud.txt owncloud11.txt, these messages
appear in the log:
[2016/11/04 14:58:05.221587,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.224368,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_CANCELLED] || at ../source3/smbd/smb2_notify.c:123
[2016/11/04 14:58:05.233427,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.233644,  2] ../source3/smbd/open.c:1006(open_file) 
DOMAIN\ricardo opened file owncloud.txt read=No write=No (numopen=2) 
[2016/11/04 14:58:05.233929,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.238914,  3] ../source3/smbd/vfs.c:1214(check_reduced_name) 
check_reduced_name: couldn't get realpath for owncloud11.txt 
[2016/11/04 14:58:05.238936,  3]
../source3/smbd/filename.c:1426(filename_convert_internal)
filename_convert_internal: check_name failed for name owncloud11.txt with
NT_STATUS_UNSUCCESSFUL
[2016/11/04 14:58:05.238963,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_UNSUCCESSFUL] || at ../source3/smbd/smb2_create.c:293
[2016/11/04 14:58:05.238992,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[5]
status[NT_STATUS_FILE_CLOSED] || at ../source3/smbd/smb2_server.c:2512
[2016/11/04 14:58:05.239985,  3]
../source3/smbd/trans2.c:8298(smbd_do_setfilepathinfo)
smbd_do_setfilepathinfo: owncloud.txt (fnum 156833062) info_level=65290
totdata=48
[2016/11/04 14:58:05.241508,  3] ../source3/smbd/vfs.c:1214(check_reduced_name) 
check_reduced_name: couldn't get realpath for owncloud11.txt 
[2016/11/04 14:58:05.241531,  3]
../source3/smbd/filename.c:1426(filename_convert_internal)
filename_convert_internal: check_name failed for name owncloud11.txt with
NT_STATUS_UNSUCCESSFUL
[2016/11/04 14:58:05.241560,  3]
../source3/smbd/smb2_server.c:3098(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
status[NT_STATUS_UNSUCCESSFUL] || at ../source3/smbd/smb2_setinfo.c:132
[2016/11/04 14:58:05.242222,  2] ../source3/smbd/close.c:783(close_normal_file) 
DOMAIN\ricardo closed file owncloud.txt (numopen=1) NT_STATUS_OK 
[2016/11/04 14:58:05.242438,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.242932,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.250632,  2] ../source3/smbd/open.c:1006(open_file) 
DOMAIN\ricardo opened file owncloud.txt read=No write=No (numopen=2) 
[2016/11/04 14:58:05.250907,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512 
[2016/11/04 14:58:05.256954,  2] ../source3/smbd/close.c:783(close_normal_file) 
DOMAIN\ricardo closed file owncloud.txt (numopen=1) NT_STATUS_OK 
[2016/11/04 14:58:05.257129,  3]
../source3/winbindd/winbindd_getgrgid.c:50(winbindd_getgrgid_send)
getgrgid 10512