Bluetooth performance depends on the devices, their antennas, and the environment between them. Start by moving the source device closer to the headphones or speaker and removing obstacles where possible. A bag, wall, or person's body can weaken a signal. Wireless congestion from nearby devices may also contribute, especially in a crowded room.
Check that both devices have enough battery and that the intended audio device is selected. Disconnect old or unused pairings if the source keeps connecting to the wrong speaker. If playback stutters, pause other demanding wireless activity nearby and test again. Updating device software can resolve compatibility issues, but make sure the update is from the manufacturer's normal update process.
When basic checks fail, remove the Bluetooth pairing from both devices and pair them again using the instructions provided. Some headphones allow connections to multiple sources, which can create confusion when a second device takes over. Turn off multipoint temporarily to test whether that is happening. If only one source has trouble, investigate its settings; if every source drops out, inspect the accessory, its battery, and its surroundings before replacing anything.