Buffer file error with GUI drag

I made a chiptune wavetable channel emulator (designed after the NES and GameBoy) with a GUI for drawing 4-bit, 32-entry waveforms. Everything runs fine, but if I drag on the mutislider view I get
“File ‘/Users/josiahsytsma/Library/Application Support/SuperCollider/tmp/352489839’ could not be opened: System error : No such file or directory.”
Why is the server throwing this error? There aren’t any issues with the server finding the correct buffer as I’m interacting with the GUI, it’s just annoying.

(
var num=32, depth=15, pad=10, size=512, pattern, player, tri, sin, saw, random1, pulse1, pulse2, pulse3, playButton;
t.stop;
s=Server.local;
s.freeAllBuffers;
x.stop;
Window.closeAll;
s.waitForBoot({
	s.scope(1);
	t=TempoClock(120/60).permanent_(true);
	pattern = Pmono(
		\wt,
		\dur, 1,
		\root, 2,
		\octave, 4,
		\scale, Scale.chromatic,
		\degree, Pseq([
			0, -1, -3, -5,
			0, -5, -3, -5,
			-1, -5, -3, -2,
			-1, -5, 0, -5,
		], inf),
		\amp, 0.5,
	);
	w = Window.new("Wavetable", Rect(500,600,430+pad+60,13*depth+pad), false).front;
	w.onClose = {s.freeAll; player.stop; Window.closeAll};
	b = Buffer.alloc(s, size * 2);
	playButton = Button(w, Rect(430, pad, 40, 20))
	.states_([["Play", Color.black, Color.green], ["Stop", Color.black, Color.red]])
	.action_({ |button|
		if(button.value == 1 and: { player.isNil or: { player.isPlaying.not } }) {
			player = pattern.play(t);
		} {
			player.stop;
			button.value = 0;
		};
	});
	m = MultiSliderView(w, Rect(pad/2, pad/2, 421, 13*depth));
	m.background=Color.fromHexString("#9bbc0f");
	m.fillColor=Color.fromHexString("#0f380f");
	m.size(num);
	m.gap_(1);
	m.step_(1/depth);
	m.action_({
		arg q;
		var env, wave;
		env=Env(q.value, 1!q.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable);
	});
	m.valueAction_(
		Array.fill(32, {
			arg i;
			7+(7.5*((pi/16)*i).sin).round(1)/15
		});
	);
	tri = Button(w, Rect(430, 43+(1.5*pad), 60, 20))
	.states_([["Triangle", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0]/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});
	sin = Button(w, Rect(430, 20+(1.5*pad), 60, 20))
	.states_([["Sine", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=Array.fill(32, {
			arg i;
			7+(7.5*((pi/16)*i).sin).round(1)/15
		});
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});
	saw = Button(w, Rect(430, 66+(1.5*pad), 60, 20))
	.states_([["Saw", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=[15,15,14,14,13,13,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3,2,2,1,1,0,0]/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});

	random1 = Button(w, Rect(430, 89+(1.5*pad)+(23*3), 60, 20))
	.states_([["Random", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=Array.rand(32,0,15)/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});

	pulse1 = Button(w, Rect(430, 89+(1.5*pad), 60, 20))
	.states_([["Pulse 1", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=((15!16)++(0!16))/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});

	pulse2 = Button(w, Rect(430, 89+(1.5*pad)+23, 60, 20))
	.states_([["Pulse 2", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=((15!8)++(0!24))/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});

	pulse2 = Button(w, Rect(430, 89+(1.5*pad)+46, 60, 20))
	.states_([["Pulse 3", Color.white, Color.fromHexString("#9a2257")]])
	.action_({
		var array, env;
		array=((15!4)++(0!28))/15;
		m.valueAction_(array);
		env=Env(array, 1!array.size, \lin);
		b.loadCollection(env.asSignal(size)
			.asWavetable)
	});

	SynthDef(\wt, {
		arg freq=440, pan=0, amp=1.0, out=0, bufnum=b, gate=1;
		var env, sig;
		sig = Osc.ar(bufnum, freq);
		env = EnvGen.ar(Env.asr(0,amp,0), gate, doneAction:2);
		sig = LeakDC.ar(sig);
		sig = sig*env;
		sig = Pan2.ar(sig, pan);
		sig = sig.round(1/2.pow(8));
		Out.ar(out, sig);
	}).add;
});
)