DirectAdmin Login Causes huge server load

Hello,
While login to directadmin control panel as admin (didn't tried as user/reseller) server load increased rapidly 0 to 5/6. From system monitor it is observed user admin usage 96-99% cpu for php command. It should be noted that recently I've upgrade vps to use multi-php version (5.6 & 7.1.5).
Please help me to solve this problem.

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