Inconsistent upload speeds in evenings at inconsistent times

For the past 2 weeks I've been having extremely inconsistent issues with my upload speeds in the evening randomly when working from home. Before I didn't have any issues since March of last year. But almost daily my upload speed seems to drop down to under 1mpbs sometime after 7PM and stays that way until 3-4AM when an outage gets called and it's fixed by morning. I say sometime because it's never the same time when it tanks. I've had it drop at 10PM and even midnight. After multiple talks with reps who have no idea what I'm saying and just want to reboot my modem I had a tech come out and unfortunately when they were here the issue wasn't active. And they aren't out after 7PM to respond when it does happen. But for a solid week after the tech visit I hadn't had a single issue with my speeds, unless they dropped early in the mornings. Then suddenly today it's right back to tanking again and it's really affecting my job since I need my upload speed to keep working from home. I've already had to miss several days because of it. I have another tech coming Saturday and tried to ask if a Senior Tech could be scheduled so hopefully I can find a fix with them. Otherwise what can I do? I would love to switch ISPs because I cannot lose my job over this but not even CenturyLink has enough speeds in my area.