[CA] What can I expect in a coworker conflict.

I have a coworker above me in the org chart with a 'Senior' title. I do not report to them but they have been given some administrative/leading style tasks: planning and delegating work, reviewing and assisting with meet goals in employee work plans.

On three separate occasions they told me I was causing issues with other staff in the department due to the way I communicate or interact. On all three occasions, I spoke with the staff in question to apologize and confess I didn't realize my interactions were concerning. On all three occasions, they had no idea what I was talking about nor did their superiors.

During this time the senior had been holding 1:1s with me monthly. When I asked my manager about them I was told I don't report to the senior so have no obligation to go to them. I shared that it seemed to make the senior happy and it's nice to chat so was happy to oblige. During the most recent one in June, senior shared that they were asked to review me monthly as they just received the annual review template and would give the reviews to our manager

This is also when they made the third claim about my interpersonal relations.

After the third occasion, I spoke with our mutual manager expressing my concern and wanting to validate my sense of the situation was accurate. Our manager assured me I'm doing a great job and that they would find out what was going on.

Shortly after, my senior informed me that their concern for my interactions wasn't a problem and that people were overreacting. A day or two after that I had my scheduled monthly 1:1 with our manager during which I told them the senior had shared with me that folks were overreacting. Our manager confirmed that they told the senior I'm doing great and they're overreacting. This was 4 weeks ago.

Our manager started a planned 5 weeks of FMLA at the end of last week.

Today was my first day in the office for the week due to my normal schedule. The acting manager asked to speak with me and informed me my senior had gone to HR and complained about my interactions with others saying I had now also offended staff outside our department. HR brought this to the acting manager who told them it would be handled internally and called me in to tell me all this.

I expressed how blind sided I was by this and provided the above context. Acting manager had no idea about any of it and said they would discuss with HR. Shortly after that I received a message that acting manager would be working with their superiors to assure the above stops for good.

Uncertain of what was discussed with HR I sat with them to share my concern about the situation and provide the extent of the above context. They were very curious about the senior's "review" of me and that the senior was advised I am not causing problems a month ago.

Senior is on vacation today until Tuesday. I'm on long scheduled PTO next week.

HR has assured me they are going to have a very "black and white" conversation with the senior in my absence and will schedule to meet with me for a couple minutes upon my return to confirm they have done this. They have assured me I should have no concerns, to think nothing of this, enjoy my vacation, and at my only kind of joking prompting, I am coming back from vacation to my job.

For context, senior has been here a couple years, I am almost 1 year.

ETA: saw acting manager at end of day and shared that I engaged with HR. They told me they were glad I did and already knew as they talked to HR in the evening as well.