ASP.NET Core Web API route issue

I have a BaseController with a route defined as follows:

[ApiController]
[Route("trac/[controller]")]
public abstract class BaseController<T> : ControllerBase

And I have another controller inheriting from it:

public class HeadingsController: BaseController<IServices>
{
    [HttpGet("{controller}")]
    public async Task<ActionResult> ByController(int controller)
        => Ok(await this.Service.ByController(controller));
    ...
}

which matches perfectly in swagger

But when testing, the route is not matched:

I tried to put [FromRoute] in front - no change.

All other routes work as expected - including body and query params.

Any suggestions on that?

managed it

param named controller causes issues

interferes with api naming convention, no issues for swagger though

changed to controllerId and all works