It is entirely possible / likely there are bugs within MacroDroid that can lead to battery drain issues like this, but it's super difficult to know what might be happening without additional information.
It could be something like a stuck wakelock and tools like GSam are useful for finding these sort of problems. It can also be misconfigured macros as was also suggested. This is very hard to quantify but the system log might indicate if something is running over and over again without much delay in the system log.
If you are able to discover any additional info then it's best directly to me at
support@macrodroid.com. I definitely do want to fix any issues that causes battery drain like this.
For any other users reading this and being concerned, I must point out that reports like this are fairly rare and I do not believe there are any major battery related issues in typical use cases.