Usually the M107 command requires a prior definition of fan indices via M106 commands. An explanation can be found here.
However, I doubt that the M107 command has been implemented properly in the Sovol stock firmware. A workaround is g-code command “M106 P1 S0” to set a speed of 0 for the right fan. Be aware that the behaviour of your SV04 will depend on its current printing mode. This issue has already been discussed here.
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