Drobo Ejects when iMac goes to sleep

I have an older 4 bay Drobo and a mid 2011 iMac running Yosemite. For awhile now when the iMac goes to sleep, the drobo ejects and sometimes will keep turning on the mac from sleep. I will turn on from sleep and ill have 5 or more messages saying the drobo wasn’t properly ejected and then after a few times the drobo will completely disconnect from the computer. Does anyone else have this issue and if so how do i fix it? Thanks!