String changes can sort it out: my G&L SB1 suffered this - even with new strings (the ones with the single reduced core, can't remember what they are called now, seemed like a good idea at the time). Setup and new (normal) strings sorted it. Another bass I have developed the dead spot recently - slackening string, lifting out of nut and bridge then reseating cured it. If the dead spot persists other tactics may work - remove neck, shim then setup again. DIY Fatfinger is as simple as block of stainless steel stuck down on headstock reverse with copydex. If it works fix more permanently.