Before revision:  To remove those critical values of \Delta t, we propose a slight modification of the original LF-LTS method which nonetheless preserves its desirable properties: it is fully explicit, second-order accurate, satisfies a three-term (leapfrog like) recurrence relation, and conserves the energy.
After revision:  To remove those critical values of \Delta t, we propose a slight modification (as in recent work on LF-Chebyshev methods \mbox{%DIFAUXCMD CarHocStu19 the original LF-LTS method which nonetheless preserves its desirable properties: it is fully explicit, second-order accurate, satisfies a three-term (leapfrog like) recurrence relation, and conserves the energy.