Failed upgrade: MySQL on WampServer -

i have tried couple of times, on separate occasions, upgrade mysql version 5.6.17 5.6.25 on wampserver.

each time upgrade unsuccessful:

fatal error: upgrade failed 

the feedback left in upgrade_result.txt file is:

looking 'mysql.exe' as: c:\wamp\bin\mysql\mysql5.6.25\bin\mysql.exe looking 'mysqlcheck.exe' as: c:\wamp\bin\mysql\mysql5.6.25\bin\mysqlcheck.exe 

both files exist. follow instructions have been able find posted in wampserver forum on 2 years ago: http://forum.wampserver.com/read.php?2,111797,124054

if knows how deal this, please let me know.