Set the length of a fill before choosing notes
Count the space available for the fill, then practice the return to the groove.
If the band leaves beats 3 and 4 for a fill in 4/4, count the whole bar before choosing the notes. As a practice example, keep the groove on beats 1 and 2, then play snare eighth notes on “3 & 4 &,” alternating R L R L. Resume the original groove on the next 1.
Loop the fill bar and the following bar with a metronome. Listen for an even gap from the last “&” to beat 1, and check that the backbeat returns where the groove needs it. Slow down if reaching for the cymbal delays the return.
This example uses two beats. A fill beginning on beat 4 uses one beat, and a song may leave another length entirely. Count the available space first, then choose the notes. If the sticking makes the return awkward, try beginning with the other hand and compare how easily you reach the cymbal on the next 1.