Algebraic loops occur when an input port with direct feedthrough is driven by the output of the same block, either directly, or by a feedback path through other blocks which have direct feedthrough. In most of the cases adding a small delay (Either discrete delay block or continuous memory block) to the system at its highest level might remove the loop. However, this can, in some situations, add unnecessary dynamics which may affect the results.
For more detailed explanation on Algebraic loops, and how they can be solved, please refer to the following MATLAB answers post: https://www.mathworks.com/matlabcentral/answers/95310-what-are-algebraic-loops-in-simulink-and-how-do-i-solve-them
Hope this helps!
