Problems with big open complexity gaps This question is about problems for which there is a big open complexity gap between known lower bound and upper bound, but not because of open problems on complexity classes themselves.

To be more precise, let's say a problem has gap classes $A,B$ (with $A\subseteq B$, not uniquely defined) if $A$ is a maximal class for which we can prove it is $A$-hard, and $B$ is a minimal known upper bound, i.e. we have an algorithm in $B$ solving the problem. This means if we end up finding out that the problem is $C$-complete with $A\subseteq C\subseteq B$, it will not impact complexity theory in general, as opposed to finding a $P$ algorithm for a $NP$-complete problem.

I am not interested in problems with $A\subseteq P$ and $B=NP$, because it is already the object of this question.

I am looking for examples of problems with gap classes that are as far as possible. To limit the scope and precise the question, I am especially interested in problems with $A\subseteq P$ and $B\supseteq EXPTIME$, meaning both membership in $P$ and $EXPTIME$-completeness are coherent with current knowledge, without making known classes collapse (say classes from this list).
The Knot Equivalence Problem. 

Given two knots drawn in the plane, are they topologically the same? This problem is known to be decidable, and there do not seem to be any computational complexity obstructions to its being in P. The best upper bound currently known on its time complexity seems to be a tower of $2$s of height $c^n$, where $c = 10^{10^{6}}$, and $n$ is the number of crossings in the knot diagrams. This comes from a bound by Coward and Lackenby on the number of Reidemeister moves needed to take one knot to an equivalent one. See Lackenby's more recent paper for some more recent related results and for 
the explicit form of the bound I give above (page 16).