Yes — the most likely cause is the optical slave setup, not the flashes themselves.

Optical slaves need to “see” the triggering flash, either directly or via reflected light. In a large space, that becomes less reliable because the flash signal has farther to travel. Large softboxes can block or shade the slave sensor, and dark or black walls reduce the reflected light that might otherwise help trigger the other heads. Bright ambient light can also make optical triggering less dependable.

The most reliable fix is to stop depending on optical slave mode and use radio triggering on all three monolights by adding matching receivers. That removes the line-of-sight issue.

Other possible workarounds are:

• reposition the lights so the optical sensors have a clear view of the triggering head
• use an external optical slave sensor on a cord so the sensor can be placed where it can see the flash
• use a simple shield or “hood” around the sensor to block stray ambient light and point it toward the master flash

For consistent studio use, full radio triggering is the best solution.