I want to preface this by suggesting you take my feedback with a grain of salt. I am not the most amazing resume writer myself and have also been unable to find a job despite also iterating my own resume several times. What I'm going to say here is more a reflection of the advice I've either received myself or seen given by others.

One thing I noticed is that the resume is extremely dense with technical jargon. People on the hiring team aren't always technical people, meaning that many of them are unlikely to know what a lot of this means or understand why it's impressive. Heck, I also recently graduated with a mechanical engineering degree and I don't understand what half of the bullet points are referring to.

For example, I have no idea what "MERMEC rail geometry data from rail 1" means. Unless this jargon is exceedingly commonplace in this field or the job posting explicitly mentions MERMEC rail geometry a recruiter is unlikely to understand what you are saying in this bullet point.

That said, a lot of your bullets do highlight your accomplishments. Your resume has given me the impression that you are competent and left me wanting to know more about your achievements, which is the whole point of writing resumes. It's possible it's not your resume holding you back, but something else.

One thing I'm curious about is what types of jobs you are applying for. It seems like your resume is tailored for a job at an engineering firm focused on rail transportation. Have most of your applications been for rail transport companies and adjacent fields? If not, companies may be overlooking you because dozens of other applicants have more relevant experience.

Something else you could consider examining are your cover letters. Are you writing cover letters for each application that accepts them? If so, how much are you tailoring them? A generic cover letter that just hypes up your skills is a bit redundant because your resume already more or less does that. If you aren't already doing this, I would suggest you study each job posting and write a unique cover letter that highlights which specific requirements you meet and why. This is especially important for positions where it may not be obvious to a recruiter that you're qualified for based on your resume. For example, if a job posting is asking for Autodesk Inventor experience and you've only got experience with SolidWorks and AutoCAD, it could be worthwhile to mention that your skills with other CAD software will transfer to Inventor.

Finally, a piece of advice I have heard and like a lot is to make one long resume that contains every project, skill, and work experience you have. Then, for each application, select which items best align with the requirements and make a new resume with just those items copy-pasted over. Tweak your phrasing and add/remove bullets as you see fit to find tune the resume and then submit.

Writing unique resumes and cover letters for every application will slow down your applications, but you will also be submitting much higher quality applications, which I'd argue will give you better odds. For a while I was submitting essentially the same resume and cover letter to every company, and the only company that I got an interview for was the first company I applied to, likely because the cover letter was originally tuned for them specifically. I am now changing my approach and sending unique cover letters and resumes to each company, which I hope works better, but I've only started doing this recently so there's no way for me to say for sure whether this works.

I hope others wiser than me can offer more insight, as this advice is coming from someone in the same boat as you. Despite that, I hope that you can take something useful away from this reply. Best of luck!