I recently got this advice that has been very useful to other bands with this same issue: include in your regular rehearsal schedule the practice of all songs without the vocals.
Seems that one of the most common and important issues is a little too much dependence in the vocalist(s). Instead of counting, some people build a dependence on the vocals as the cue to everything. This can lead to complete lack of counting, and the dependence gets stronger with each rehearsal.
This doesn't need to be intentional. Sometimes it's only until you have lost that reference that you notice how dependent you were. "I can't hear the vocals, I don't know which part of the song we are supposed to be playing". It's too late by then.
Including practice without vocals gets you back to the basics. It's important to pay the most attention to the counting, rather than building new cue references with other instruments. Knowing other instrument cues is very helpful, so don't ignore that new information, just don't go back to that dependence and give the priority to counting instead.
"Counting" doesn't need to be the literal acknowledgement of every beat and bar; it can be "play two times this, then three times that". Count with the abstraction level you feel comfortable with.
The intention is to build references around everything and nothing. Know the cues of every instrument (if any), and also be able to play without any reference at all. The goal is to be 100% certain of where you are in the song, regardless of the monitoring conditions.
I found that some people go beyond that and also practice every song by themselves, having counting as the only reference. This might come as a "you don't say" advice for some of us that commonly implement time in our practice and playing, but there are countless solid musicians out there that have never played with a metronome, or that never count in their heads. They just play, and it all comes out naturally. This advice is particularly useful for them.